1. Sketching a Parabola if the x-Intercepts Exist

2. What do you Need to Sketch a Parabola?
Can you sketch a parabola if you only know where its y-intercept is? For example, if the y-intercept of a parabola is (0,-15) can you sketch the graph? Why or why not?
NO!
You can NOT determine whether it opens up or down.

3. What do you Need to Sketch a Parabola?
Can you sketch a parabola if you only know where its x-intercept are? For example, if the x-intercepts of a parabola are (-3,0) and (5,0) can you sketch the graph? Why or why not?
NO!
You can NOT determine whether it opens up or down.

4. What do you Need to Sketch a Parabola?
Can you sketch a parabola if you only know where its x-intercept and y-intercept are? For example, if the x-intercepts of a parabola are (-3,0) and (5,0) and the y-intercept is (0,-15), can you sketch the graph? Why or why not?
YES!
IMPORTANT: The vertex must lie on the line of symmetry.
A third point helps determine whether it opens up or down.

5. Sketching a Quadratics
Find the y-intercept
Sketch: y = 2x2 + 5x – 12
Pay attention to Symmetry 8
Factor to find the x-intercepts -6 6
Draw the Parabola
-16