{"id":679,"date":"2025-07-14T21:00:23","date_gmt":"2025-07-14T21:00:23","guid":{"rendered":"https:\/\/content.one.lumenlearning.com\/precalculus\/?post_type=chapter&#038;p=679"},"modified":"2025-12-15T21:35:35","modified_gmt":"2025-12-15T21:35:35","slug":"module-3-linear-functions-cheat-sheet","status":"publish","type":"chapter","link":"https:\/\/content.one.lumenlearning.com\/precalculus\/chapter\/module-3-linear-functions-cheat-sheet\/","title":{"raw":"Linear Functions: Cheat Sheet","rendered":"Linear Functions: Cheat Sheet"},"content":{"raw":"<h2 class=\"text-text-100 mt-3 -mb-1 text-[1.125rem] font-bold\">Essential Concepts<\/h2>\r\n<h3 class=\"text-text-100 mt-2 -mb-1 text-base font-bold\">Graphs of Linear Functions<\/h3>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">A <strong>linear function<\/strong> is a function with a constant rate of change, represented by a polynomial of degree 1. Its graph is always a straight line.<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Key Features of Linear Graphs<\/strong><\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Slope (m):<\/strong> The rate of change, showing how steep the line is\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Positive slope: line rises from left to right (increasing function)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Negative slope: line falls from left to right (decreasing function)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Zero slope: horizontal line (constant function)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Undefined slope: vertical line<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>y-intercept (b):<\/strong> The point where the line crosses the y-axis, written as [latex](0, b)[\/latex]\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Find by setting [latex]x = 0[\/latex] in the equation<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Represents the initial value or starting point<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>x-intercept:<\/strong> The point where the line crosses the x-axis, written as [latex](a, 0)[\/latex]\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Find by setting [latex]y = 0[\/latex] and solving for [latex]x[\/latex]<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Not all linear functions have an x-intercept (horizontal lines like [latex]y = 5[\/latex] do not)<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">Slope measures how one quantity changes in relation to another:<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">[latex]m = \\dfrac{\\text{change in output}}{\\text{change in input}} = \\dfrac{\\text{rise}}{\\text{run}} = \\dfrac{y_2 - y_1}{x_2 - x_1}[\/latex]<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">The units of slope are \"output units per input unit\" (like miles per hour or dollars per year).<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Graphing by Plotting Points<\/strong><\/p>\r\n\r\n<ol class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-decimal flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Choose at least two input values (three is better to check for errors)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Evaluate the function at each input<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Plot the coordinate pairs<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Draw a line through the points<\/li>\r\n<\/ol>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Graphing Using Slope and y-intercept<\/strong><\/p>\r\n\r\n<ol class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-decimal flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Find the y-intercept and plot that point<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Use the slope [latex]\\frac{\\text{rise}}{\\text{run}}[\/latex] to find additional points<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Draw a line through the points<\/li>\r\n<\/ol>\r\n<h3 class=\"text-text-100 mt-2 -mb-1 text-base font-bold\">Linear Functions<\/h3>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Three Forms of Linear Equations<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Slope-Intercept Form:<\/strong> [latex]y = mx + b[\/latex]<\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">[latex]m[\/latex] is the slope<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">[latex]b[\/latex] is the y-intercept<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Most common form for graphing<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Point-Slope Form:<\/strong> [latex]y - y_1 = m(x - x_1)[\/latex]<\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">[latex]m[\/latex] is the slope<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">[latex](x_1, y_1)[\/latex] is a point on the line<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Useful when you know the slope and one point<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Standard Form:<\/strong> [latex]Ax + By = C[\/latex]<\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">[latex]A[\/latex], [latex]B[\/latex], and [latex]C[\/latex] are integers<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">[latex]A[\/latex] and [latex]B[\/latex] are not both zero<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Useful for certain applications<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Writing Equations of Lines<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Given two points:<\/strong><\/p>\r\n\r\n<ol class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-decimal flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Calculate slope: [latex]m = \\frac{y_2 - y_1}{x_2 - x_1}[\/latex]<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Use point-slope form with either point<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Simplify to slope-intercept form<\/li>\r\n<\/ol>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Given a graph:<\/strong><\/p>\r\n\r\n<ol class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-decimal flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Identify two clear points on the line<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Calculate the slope<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Identify the y-intercept (or use point-slope form)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Write the equation<\/li>\r\n<\/ol>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Horizontal and Vertical Lines<\/strong><\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Horizontal line:<\/strong> [latex]y = c[\/latex] (slope = 0)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Vertical line:<\/strong> [latex]x = c[\/latex] (slope is undefined)<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Parallel and Perpendicular Lines<\/strong><\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Parallel lines:<\/strong> Have the same slope but different y-intercepts\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">If line 1 has slope [latex]m[\/latex], a parallel line also has slope [latex]m[\/latex]<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Perpendicular lines:<\/strong> Have slopes that are negative reciprocals\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">If line 1 has slope [latex]m[\/latex], a perpendicular line has slope [latex]-\\frac{1}{m}[\/latex]<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Exception: Horizontal and vertical lines are perpendicular to each other<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Parallel and Perpendicular to Horizontal or Vertical Lines:<\/strong><\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">A line parallel to [latex]y = c[\/latex] is [latex]y = d[\/latex] (another horizontal line)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">A line parallel to [latex]x = c[\/latex] is [latex]x = d[\/latex] (another vertical line)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">A line perpendicular to [latex]y = c[\/latex] is [latex]x = d[\/latex] (vertical)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">A line perpendicular to [latex]x = c[\/latex] is [latex]y = d[\/latex] (horizontal)<\/li>\r\n<\/ul>\r\n<h3 class=\"text-text-100 mt-2 -mb-1 text-base font-bold\">Linear Models<\/h3>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Building Linear Models from Word Problems<\/strong><\/p>\r\n\r\n<ol class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-decimal flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Identify changing quantities and define variables<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Determine the initial value (y-intercept)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Determine the rate of change (slope)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Write the equation using [latex]y = mx + b[\/latex]<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Use the model to make predictions or solve problems<\/li>\r\n<\/ol>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Scatter Plots and Lines of Best Fit<\/strong><\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Scatter plot:<\/strong> A graph of data points that may show a relationship between two variables<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Linear relationship:<\/strong> Points form a pattern resembling a straight line<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Line of best fit:<\/strong> A line that best represents the trend in the data\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Can be estimated by sketching<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Can be calculated precisely using linear regression<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Interpolation vs. Extrapolation<\/strong><\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Interpolation:<\/strong> Predicting a value inside the domain and range of the data\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Generally more reliable<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Extrapolation:<\/strong> Predicting a value outside the domain and range of the data\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Less reliable; may lead to inaccurate predictions<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h3 class=\"text-text-100 mt-2 -mb-1 text-base font-bold\">Absolute Value Functions<\/h3>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Absolute value<\/strong> measures distance from zero on a number line, always non-negative: [latex]|x| = \\begin{cases} x &amp; \\text{if } x \\geq 0 \\ -x &amp; \\text{if } x &lt; 0 \\end{cases}[\/latex]<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Graphing Absolute Value Functions<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">The basic absolute value function [latex]f(x) = |x|[\/latex] has a V-shape with a corner point at the origin. It can be transformed using:<\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Vertical\/horizontal shifts<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Vertical\/horizontal stretches or compressions<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Reflections across the x-axis or y-axis<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Solving Absolute Value Equations<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">For [latex]|A| = B[\/latex] where [latex]B \\geq 0[\/latex]:<\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Set up two equations: [latex]A = B[\/latex] or [latex]A = -B[\/latex]<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Solve each equation<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">Check solutions in the original equation<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">Special cases:<\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">If [latex]B &lt; 0[\/latex]: No solution (absolute value cannot be negative)<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">If [latex]B = 0[\/latex]: One solution<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">If [latex]B &gt; 0[\/latex]: Two solutions (usually)<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Solving Absolute Value Inequalities<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">For [latex]|X| &lt; k[\/latex] where [latex]k &gt; 0[\/latex]:<\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Equivalent to [latex]-k &lt; X &lt; k[\/latex]<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Interval notation:<\/strong> [latex](-k, k)[\/latex]<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">For [latex]|X| &gt; k[\/latex] where [latex]k &gt; 0[\/latex]:<\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">Equivalent to [latex]X &lt; -k[\/latex] or [latex]X &gt; k[\/latex]<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\"><strong>Interval notation:<\/strong> [latex](-\\infty, -k) \\cup (k, \\infty)[\/latex]<\/li>\r\n<\/ul>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">Same logic applies for [latex]\\leq[\/latex] and [latex]\\geq[\/latex]:<\/p>\r\n\r\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\r\n \t<li class=\"whitespace-normal break-words pl-2\">[latex]|X| \\leq k[\/latex] gives [latex][-k, k][\/latex]<\/li>\r\n \t<li class=\"whitespace-normal break-words pl-2\">[latex]|X| \\geq k[\/latex] gives [latex](-\\infty, -k] \\cup [k, \\infty)[\/latex]<\/li>\r\n<\/ul>\r\n<h2 class=\"text-text-100 mt-3 -mb-1 text-[1.125rem] font-bold\">Key Equations<\/h2>\r\n<table style=\"width: 58.8277%;\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 30.4996%;\"><strong>Slope formula<\/strong><\/td>\r\n<td style=\"width: 136.163%;\">[latex]m = \\frac{y_2 - y_1}{x_2 - x_1}[\/latex]<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 30.4996%;\"><strong>Slope-intercept form of a line<\/strong><\/td>\r\n<td style=\"width: 136.163%;\">[latex]y = mx + b[\/latex]<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 30.4996%;\"><strong>Point-slope form of a line<\/strong><\/td>\r\n<td style=\"width: 136.163%;\">[latex]y - y_1 = m(x - x_1)[\/latex]<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 30.4996%;\"><strong>Standard form of a line<\/strong><\/td>\r\n<td style=\"width: 136.163%;\">[latex]Ax + By = C[\/latex]<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<h2 class=\"text-text-100 mt-3 -mb-1 text-[1.125rem] font-bold\">Glossary<\/h2>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>absolute value<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the distance of a number from zero on the number line, always non-negative; denoted [latex]|x|[\/latex]<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>absolute value equation<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">an equation of the form [latex]|A| = B[\/latex] with [latex]B \\geq 0[\/latex]; has solutions when [latex]A = B[\/latex] or [latex]A = -B[\/latex]<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>absolute value inequality<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a relationship in the form [latex]|A| &lt; B[\/latex], [latex]|A| \\leq B[\/latex], [latex]|A| &gt; B[\/latex], or [latex]|A| \\geq B[\/latex]<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>decreasing linear function<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a linear function with a negative slope; as input increases, output decreases<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>extrapolation<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">predicting a value outside the domain and range of observed data<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>horizontal line<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a line defined by [latex]y = b[\/latex] where [latex]b[\/latex] is a constant; has slope of 0<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>increasing linear function<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a linear function with a positive slope; as input increases, output also increases<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>interpolation<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">predicting a value inside the domain and range of observed data<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>linear function<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a function with a constant rate of change, represented as a polynomial of degree 1; graph is a straight line<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>line of best fit<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a line that best represents the trend in a set of data points; can be found using linear regression<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>parallel lines<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">two or more lines with the same slope<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>perpendicular lines<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">two lines that intersect at right angles and have slopes that are negative reciprocals of each other<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>point-slope form<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the equation of a line in the form [latex]y - y_1 = m(x - x_1)[\/latex] where [latex]m[\/latex] is the slope and [latex](x_1, y_1)[\/latex] is a point on the line<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>scatter plot<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a graph of plotted points that may show a relationship between two sets of data<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>slope<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the ratio of the change in output to the change in input; measures the steepness and direction of a line; calculated as [latex]m = \\frac{y_2 - y_1}{x_2 - x_1}[\/latex]<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>slope-intercept form<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the equation of a line in the form [latex]y = mx + b[\/latex] where [latex]m[\/latex] is the slope and [latex]b[\/latex] is the y-intercept<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>standard form<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the equation of a line in the form [latex]Ax + By = C[\/latex] where [latex]A[\/latex], [latex]B[\/latex], and [latex]C[\/latex] are integers<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>vertical line<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a line defined by [latex]x = a[\/latex] where [latex]a[\/latex] is a constant; has undefined slope<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>x-intercept<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the point where a graph crosses the x-axis; has coordinates [latex](a, 0)[\/latex]<\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>y-intercept<\/strong><\/p>\r\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the point where a graph crosses the y-axis; has coordinates [latex](0, b)[\/latex]; also called the initial value<\/p>","rendered":"<h2 class=\"text-text-100 mt-3 -mb-1 text-[1.125rem] font-bold\">Essential Concepts<\/h2>\n<h3 class=\"text-text-100 mt-2 -mb-1 text-base font-bold\">Graphs of Linear Functions<\/h3>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">A <strong>linear function<\/strong> is a function with a constant rate of change, represented by a polynomial of degree 1. Its graph is always a straight line.<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Key Features of Linear Graphs<\/strong><\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\"><strong>Slope (m):<\/strong> The rate of change, showing how steep the line is\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Positive slope: line rises from left to right (increasing function)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Negative slope: line falls from left to right (decreasing function)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Zero slope: horizontal line (constant function)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Undefined slope: vertical line<\/li>\n<\/ul>\n<\/li>\n<li class=\"whitespace-normal break-words pl-2\"><strong>y-intercept (b):<\/strong> The point where the line crosses the y-axis, written as [latex](0, b)[\/latex]\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Find by setting [latex]x = 0[\/latex] in the equation<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Represents the initial value or starting point<\/li>\n<\/ul>\n<\/li>\n<li class=\"whitespace-normal break-words pl-2\"><strong>x-intercept:<\/strong> The point where the line crosses the x-axis, written as [latex](a, 0)[\/latex]\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Find by setting [latex]y = 0[\/latex] and solving for [latex]x[\/latex]<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Not all linear functions have an x-intercept (horizontal lines like [latex]y = 5[\/latex] do not)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">Slope measures how one quantity changes in relation to another:<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">[latex]m = \\dfrac{\\text{change in output}}{\\text{change in input}} = \\dfrac{\\text{rise}}{\\text{run}} = \\dfrac{y_2 - y_1}{x_2 - x_1}[\/latex]<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">The units of slope are &#8220;output units per input unit&#8221; (like miles per hour or dollars per year).<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Graphing by Plotting Points<\/strong><\/p>\n<ol class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-decimal flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Choose at least two input values (three is better to check for errors)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Evaluate the function at each input<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Plot the coordinate pairs<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Draw a line through the points<\/li>\n<\/ol>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Graphing Using Slope and y-intercept<\/strong><\/p>\n<ol class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-decimal flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Find the y-intercept and plot that point<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Use the slope [latex]\\frac{\\text{rise}}{\\text{run}}[\/latex] to find additional points<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Draw a line through the points<\/li>\n<\/ol>\n<h3 class=\"text-text-100 mt-2 -mb-1 text-base font-bold\">Linear Functions<\/h3>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Three Forms of Linear Equations<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Slope-Intercept Form:<\/strong> [latex]y = mx + b[\/latex]<\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">[latex]m[\/latex] is the slope<\/li>\n<li class=\"whitespace-normal break-words pl-2\">[latex]b[\/latex] is the y-intercept<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Most common form for graphing<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Point-Slope Form:<\/strong> [latex]y - y_1 = m(x - x_1)[\/latex]<\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">[latex]m[\/latex] is the slope<\/li>\n<li class=\"whitespace-normal break-words pl-2\">[latex](x_1, y_1)[\/latex] is a point on the line<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Useful when you know the slope and one point<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Standard Form:<\/strong> [latex]Ax + By = C[\/latex]<\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">[latex]A[\/latex], [latex]B[\/latex], and [latex]C[\/latex] are integers<\/li>\n<li class=\"whitespace-normal break-words pl-2\">[latex]A[\/latex] and [latex]B[\/latex] are not both zero<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Useful for certain applications<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Writing Equations of Lines<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Given two points:<\/strong><\/p>\n<ol class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-decimal flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Calculate slope: [latex]m = \\frac{y_2 - y_1}{x_2 - x_1}[\/latex]<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Use point-slope form with either point<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Simplify to slope-intercept form<\/li>\n<\/ol>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Given a graph:<\/strong><\/p>\n<ol class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-decimal flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Identify two clear points on the line<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Calculate the slope<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Identify the y-intercept (or use point-slope form)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Write the equation<\/li>\n<\/ol>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Horizontal and Vertical Lines<\/strong><\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\"><strong>Horizontal line:<\/strong> [latex]y = c[\/latex] (slope = 0)<\/li>\n<li class=\"whitespace-normal break-words pl-2\"><strong>Vertical line:<\/strong> [latex]x = c[\/latex] (slope is undefined)<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Parallel and Perpendicular Lines<\/strong><\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\"><strong>Parallel lines:<\/strong> Have the same slope but different y-intercepts\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">If line 1 has slope [latex]m[\/latex], a parallel line also has slope [latex]m[\/latex]<\/li>\n<\/ul>\n<\/li>\n<li class=\"whitespace-normal break-words pl-2\"><strong>Perpendicular lines:<\/strong> Have slopes that are negative reciprocals\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">If line 1 has slope [latex]m[\/latex], a perpendicular line has slope [latex]-\\frac{1}{m}[\/latex]<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Exception: Horizontal and vertical lines are perpendicular to each other<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Parallel and Perpendicular to Horizontal or Vertical Lines:<\/strong><\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">A line parallel to [latex]y = c[\/latex] is [latex]y = d[\/latex] (another horizontal line)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">A line parallel to [latex]x = c[\/latex] is [latex]x = d[\/latex] (another vertical line)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">A line perpendicular to [latex]y = c[\/latex] is [latex]x = d[\/latex] (vertical)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">A line perpendicular to [latex]x = c[\/latex] is [latex]y = d[\/latex] (horizontal)<\/li>\n<\/ul>\n<h3 class=\"text-text-100 mt-2 -mb-1 text-base font-bold\">Linear Models<\/h3>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Building Linear Models from Word Problems<\/strong><\/p>\n<ol class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-decimal flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Identify changing quantities and define variables<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Determine the initial value (y-intercept)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Determine the rate of change (slope)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Write the equation using [latex]y = mx + b[\/latex]<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Use the model to make predictions or solve problems<\/li>\n<\/ol>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Scatter Plots and Lines of Best Fit<\/strong><\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\"><strong>Scatter plot:<\/strong> A graph of data points that may show a relationship between two variables<\/li>\n<li class=\"whitespace-normal break-words pl-2\"><strong>Linear relationship:<\/strong> Points form a pattern resembling a straight line<\/li>\n<li class=\"whitespace-normal break-words pl-2\"><strong>Line of best fit:<\/strong> A line that best represents the trend in the data\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Can be estimated by sketching<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Can be calculated precisely using linear regression<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Interpolation vs. Extrapolation<\/strong><\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\"><strong>Interpolation:<\/strong> Predicting a value inside the domain and range of the data\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Generally more reliable<\/li>\n<\/ul>\n<\/li>\n<li class=\"whitespace-normal break-words pl-2\"><strong>Extrapolation:<\/strong> Predicting a value outside the domain and range of the data\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Less reliable; may lead to inaccurate predictions<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3 class=\"text-text-100 mt-2 -mb-1 text-base font-bold\">Absolute Value Functions<\/h3>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Absolute value<\/strong> measures distance from zero on a number line, always non-negative: [latex]|x| = \\begin{cases} x & \\text{if } x \\geq 0 \\ -x & \\text{if } x < 0 \\end{cases}[\/latex]<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Graphing Absolute Value Functions<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">The basic absolute value function [latex]f(x) = |x|[\/latex] has a V-shape with a corner point at the origin. It can be transformed using:<\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Vertical\/horizontal shifts<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Vertical\/horizontal stretches or compressions<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Reflections across the x-axis or y-axis<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Solving Absolute Value Equations<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">For [latex]|A| = B[\/latex] where [latex]B \\geq 0[\/latex]:<\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Set up two equations: [latex]A = B[\/latex] or [latex]A = -B[\/latex]<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Solve each equation<\/li>\n<li class=\"whitespace-normal break-words pl-2\">Check solutions in the original equation<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">Special cases:<\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">If [latex]B < 0[\/latex]: No solution (absolute value cannot be negative)<\/li>\n<li class=\"whitespace-normal break-words pl-2\">If [latex]B = 0[\/latex]: One solution<\/li>\n<li class=\"whitespace-normal break-words pl-2\">If [latex]B > 0[\/latex]: Two solutions (usually)<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>Solving Absolute Value Inequalities<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">For [latex]|X| < k[\/latex] where [latex]k > 0[\/latex]:<\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Equivalent to [latex]-k < X < k[\/latex]<\/li>\n<li class=\"whitespace-normal break-words pl-2\"><strong>Interval notation:<\/strong> [latex](-k, k)[\/latex]<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">For [latex]|X| > k[\/latex] where [latex]k > 0[\/latex]:<\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">Equivalent to [latex]X < -k[\/latex] or [latex]X > k[\/latex]<\/li>\n<li class=\"whitespace-normal break-words pl-2\"><strong>Interval notation:<\/strong> [latex](-\\infty, -k) \\cup (k, \\infty)[\/latex]<\/li>\n<\/ul>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\">Same logic applies for [latex]\\leq[\/latex] and [latex]\\geq[\/latex]:<\/p>\n<ul class=\"[li_&amp;]:mb-0 [li_&amp;]:mt-1.5 [li_&amp;]:gap-1.5 [&amp;:not(:last-child)_ul]:pb-1 [&amp;:not(:last-child)_ol]:pb-1 list-disc flex flex-col gap-2 pl-8 mb-3\">\n<li class=\"whitespace-normal break-words pl-2\">[latex]|X| \\leq k[\/latex] gives [latex][-k, k][\/latex]<\/li>\n<li class=\"whitespace-normal break-words pl-2\">[latex]|X| \\geq k[\/latex] gives [latex](-\\infty, -k] \\cup [k, \\infty)[\/latex]<\/li>\n<\/ul>\n<h2 class=\"text-text-100 mt-3 -mb-1 text-[1.125rem] font-bold\">Key Equations<\/h2>\n<table style=\"width: 58.8277%;\">\n<tbody>\n<tr>\n<td style=\"width: 30.4996%;\"><strong>Slope formula<\/strong><\/td>\n<td style=\"width: 136.163%;\">[latex]m = \\frac{y_2 - y_1}{x_2 - x_1}[\/latex]<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 30.4996%;\"><strong>Slope-intercept form of a line<\/strong><\/td>\n<td style=\"width: 136.163%;\">[latex]y = mx + b[\/latex]<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 30.4996%;\"><strong>Point-slope form of a line<\/strong><\/td>\n<td style=\"width: 136.163%;\">[latex]y - y_1 = m(x - x_1)[\/latex]<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 30.4996%;\"><strong>Standard form of a line<\/strong><\/td>\n<td style=\"width: 136.163%;\">[latex]Ax + By = C[\/latex]<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2 class=\"text-text-100 mt-3 -mb-1 text-[1.125rem] font-bold\">Glossary<\/h2>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>absolute value<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the distance of a number from zero on the number line, always non-negative; denoted [latex]|x|[\/latex]<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>absolute value equation<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">an equation of the form [latex]|A| = B[\/latex] with [latex]B \\geq 0[\/latex]; has solutions when [latex]A = B[\/latex] or [latex]A = -B[\/latex]<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>absolute value inequality<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a relationship in the form [latex]|A| < B[\/latex], [latex]|A| \\leq B[\/latex], [latex]|A| > B[\/latex], or [latex]|A| \\geq B[\/latex]<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>decreasing linear function<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a linear function with a negative slope; as input increases, output decreases<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>extrapolation<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">predicting a value outside the domain and range of observed data<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>horizontal line<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a line defined by [latex]y = b[\/latex] where [latex]b[\/latex] is a constant; has slope of 0<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>increasing linear function<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a linear function with a positive slope; as input increases, output also increases<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>interpolation<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">predicting a value inside the domain and range of observed data<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>linear function<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a function with a constant rate of change, represented as a polynomial of degree 1; graph is a straight line<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>line of best fit<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a line that best represents the trend in a set of data points; can be found using linear regression<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>parallel lines<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">two or more lines with the same slope<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>perpendicular lines<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">two lines that intersect at right angles and have slopes that are negative reciprocals of each other<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>point-slope form<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the equation of a line in the form [latex]y - y_1 = m(x - x_1)[\/latex] where [latex]m[\/latex] is the slope and [latex](x_1, y_1)[\/latex] is a point on the line<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>scatter plot<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a graph of plotted points that may show a relationship between two sets of data<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>slope<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the ratio of the change in output to the change in input; measures the steepness and direction of a line; calculated as [latex]m = \\frac{y_2 - y_1}{x_2 - x_1}[\/latex]<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>slope-intercept form<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the equation of a line in the form [latex]y = mx + b[\/latex] where [latex]m[\/latex] is the slope and [latex]b[\/latex] is the y-intercept<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>standard form<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the equation of a line in the form [latex]Ax + By = C[\/latex] where [latex]A[\/latex], [latex]B[\/latex], and [latex]C[\/latex] are integers<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>vertical line<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">a line defined by [latex]x = a[\/latex] where [latex]a[\/latex] is a constant; has undefined slope<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>x-intercept<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the point where a graph crosses the x-axis; has coordinates [latex](a, 0)[\/latex]<\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\"><strong>y-intercept<\/strong><\/p>\n<p class=\"font-claude-response-body break-words whitespace-normal leading-[1.7]\" style=\"padding-left: 40px;\">the point where a graph crosses the y-axis; has coordinates [latex](0, b)[\/latex]; also called the initial value<\/p>\n","protected":false},"author":67,"menu_order":1,"template":"","meta":{"_candela_citation":"[]","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"part":61,"module-header":"cheat_sheet","content_attributions":[],"internal_book_links":[],"video_content":null,"cc_video_embed_content":{"cc_scripts":"","media_targets":[]},"try_it_collection":null,"_links":{"self":[{"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/pressbooks\/v2\/chapters\/679"}],"collection":[{"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/wp\/v2\/users\/67"}],"version-history":[{"count":9,"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/pressbooks\/v2\/chapters\/679\/revisions"}],"predecessor-version":[{"id":5096,"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/pressbooks\/v2\/chapters\/679\/revisions\/5096"}],"part":[{"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/pressbooks\/v2\/parts\/61"}],"metadata":[{"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/pressbooks\/v2\/chapters\/679\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/wp\/v2\/media?parent=679"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/pressbooks\/v2\/chapter-type?post=679"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/wp\/v2\/contributor?post=679"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/content.one.lumenlearning.com\/precalculus\/wp-json\/wp\/v2\/license?post=679"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}