Graphing Quadratic Functions
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This document discusses how to graph quadratic functions by finding the axis of symmetry, vertex, and y-intercept. The axis of symmetry is located at x = -b/2a. The vertex is found by plugging the x-coordinate from the axis of symmetry into the original function. The y-intercept is simply the constant term c. Graphing involves marking the axis of symmetry, vertex, y-intercept, and sketching the basic quadratic shape.
Graphing Quadratic Functions
- 1. Graphing Quadratic Functions y = ax 2 + bx + c 06/01/09 Bitsy Griffin 7.3
- 2. 1. Find the Axis of Symmetry y = ax 2 + bx + c What are we adding today? Where was the axis of symmetry yesterday in each graph? When the bx is added, the axis shifts left or right. 06/01/09 Bitsy Griffin 7.3
- 3. 2. Find the Axis of Symmetry The axis of symmetry is located at x = –b/2a Memorize it! This is also the x coordinate of the vertex. 06/01/09 Bitsy Griffin 7.3
- 4. 3. Find the Axis of Symmetry Find the axis of symmetry for y = 5 – 4x – x 2 x = - (-4)/2(-1) x = -2 06/01/09 Bitsy Griffin 7.3
- 5. 4. Find the Vertex Now that you know the x coordinate for the vertex, plug it into your function and solve for y y = 5 – 4(-2) – (-2) 2 y = 9 The vertex is located at (-2,9) 06/01/09 Bitsy Griffin 7.3
- 6. 5. Find the y-intercept This part is easy What is x when the graph crosses y? Make x = 0 and solve for y What do you notice? The y-intercept is c! 06/01/09 Bitsy Griffin 7.3
- 7. 6. Graphing Mark: Line of symmetry Vertex Downwards or upwards Basic shape using A (if needed) Intercept (and opposite) Graph 06/01/09 Bitsy Griffin 7.3