1. Graphing Parabolas Using the Vertex Axis of Symmetry & y-Intercept By: Jeffrey Bivin Lake Zurich High School jeff.bivin@lz95.org

2. Graphing Parabolas y = x 2 + 4x - 7 With your graphing calculator, graph each of the following quadratic equations and identify the vertex and axis of symmetry. y = 2x 2 + 10x + 4 y = -3x 2 + 5x + 9

3. Graph the following parabola y = x 2 + 4x - 7 axis of symmetry: vertex: y-intercept:

4. Graph the following parabola y = 2x 2 + 10x + 4 axis of symmetry: vertex: y-intercept:

5. Graph the following parabola y = -3x 2 + 5x + 9 axis of symmetry: vertex: y-intercept:

6. Graphing Parabolas y = x 2 + 4x - 7 Now look at the coefficients of the equation and the value of the axis of symmetry – especially a and b y = ax 2 + bx + c y = 2x 2 + 10x + 4 y = -3x 2 + 5x + 9

7. Graphing Parabolas y = ax 2 + bx + c Vertex: Axis of symmetry:

8. Graph the following parabola y = x 2 + 4x - 7 axis of symmetry: vertex: y-intercept:

9. Graph the following parabola y = 2x 2 + 10x + 4 axis of symmetry: vertex: y-intercept:

10. Graph the following parabola y = -3x 2 + 5x + 9 axis of symmetry: vertex: y-intercept: Why did this parabola open downward instead of upward as did the previous two?

11. Graph the following parabola y = x 2 + 6x - 8 Axis of symmetry: Vertex: y-intercept:

12. Graph the following parabola y = -2x 2 + 7x + 12 Axis of symmetry: Vertex: y-intercept:

13. Some Web Sites http://www.xahlee.org/SpecialPlaneCurves_dir/Parabola_dir/parabolaReflect.mov