Analytical Applications of Derivatives: Background You’ll Need 1

  • Recognize key features of a parabola’s graph: vertex, axis of symmetry, y-intercept, and minimum or maximum value

Key Features of a Parabola’s Graph

The graph of a quadratic function is a U-shaped curve called a parabola. Some key features of a parabola are:

  • Vertex: The extreme point of the parabola.
    • Minimum Value: Vertex is the lowest point (parabola opens upwards).
    • Maximum Value: Vertex is the highest point (parabola opens downwards).
  • Axis of Symmetry: A vertical line through the vertex dividing the parabola into two mirror images.
  • Intercepts:
    • Y-intercept: Point where the graph crosses the [latex]y[/latex]-axis. 
    • X-intercepts: Points where the graph crosses the [latex]x[/latex]-axis (zeros or roots of the quadratic function). 
Graph of a parabola showing where the x and y intercepts, vertex, and axis of symmetry are.

key features of a parabola

  • Vertex: The highest or lowest point, indicating a maximum or minimum value.
  • Axis of Symmetry: A vertical line that divides the parabola into two symmetric parts.
  • Intercepts:
    • Y-intercept: The point where the parabola crosses the [latex]y[/latex]-axis.
    • X-intercepts: The points where the parabola crosses the [latex]x[/latex]-axis, representing the roots of the quadratic equation.

The places where a function’s graph crosses the horizontal axis are the places where the function value equals zero. These values are called meaning names such as horizontal intercepts, [latex]x[/latex]-intercepts, or the zeros of the graph. They can also be referred to as the roots of a function.

Determine the vertex, axis of symmetry, zeros, and [latex]y[/latex]-intercept of the parabola shown below.

Graph of a parabola with a vertex at (3, 1) and a y-intercept at (0, 7).