You will graph a quadratic function given in vertex form by determining the vertex, axis of symmetry, orientation, and intercepts.
After completing this tutorial, you will be able to complete the following:
The x- and y-intercepts are often useful when graphing quadratic functions.
In addition to the vertex and axis of symmetry, the points where the parabola crosses the x- and y-axis are often used when graphing quadratic functions; these points are referred to as the x- and y-intercepts, respectively.
The easiest method of calculating the y-intercept, using the vertex form of the quadratic function, is to evaluate f(0). Using the above example, f(0) = 2(0 + 2)^2 - 3 = 5, the y-intercept of the quadratic function f(x) = 2(x + 2)^2 - 3 is the point on the y-axis (0, 5). It should be noted, that for a relationship to be a function, the function can have only one y-intercept.
While, calculating the y-intercept is straight forward, the same cannot be said of about the x-intercept. There are three possible scenarios, which can occur when graphing parabolas, that determine if and how many x-intercepts exist:
1. The graph of the parabola does not cross the x-axis and hence no x-intercepts exist (this happens when the vertex of the parabola lies above the x-axis and opens upward or when the vertex lies below the x-axis and opens downward).
2. The graph crosses the x-axis at two points (when the parabola lies below the x-axis and opens upward or when the vertex lies above the x-axis and opens downward).
3. The graph touches the x-axis at one point, which is also the vertex of the parabola (this happen when k = 0).
If the zeros of a function are real numbers, calculate the x-values when f(x) = 0.
|Approximate Time||25 Minutes|
|Pre-requisite Concepts||Students should understand the concepts of axis of symmetry, evaluating functions, orientation of a quadratic function, parabola, quadratic, quadratic function in vertex form, solving linear equations vertex, xintercept, yintercept.|
|Type of Tutorial||Procedural Development|
|Key Vocabulary||axis of symmetry, graph of a quadratic function, quadratic function in vertex form|