1. Graph and Write Equations of Parabolas
SECTION 9.2
Graph and Write Equations of Parabolas

2. California Standard:
16.0: Students demonstrate and explain how the geometry of a conic section depends on the coefficient of the quadratic equation representing it.

3. OBJECTIVE(S): By following instructions, students will be able to:
Graph and write equations of parabolas that open left or right.

5. PARABOLAS IN REAL LIFE

6. CIRCLES IN REAL LIFE

7. ELLIPSES IN REAL LIFE

8. HYPERBOLAS IN REAL LIFE

9. Def: Each point on any parabola is equidistant from a point called the focus and a line called the directrix.
Focus lies on the axis of symmetry.
Vertex lies halfway between the focus and the directrix.
The directrix is perpendicular o the axis of symmetry.

10. The equation of a parabola that opens up or down and has vertex (0,0) can also be written as .
The equation of a parabola that opens left or right and has vertex (0,0) has the equation

11. Equation
Focus
Directrix
Axis of Symmetry

12. EXAMPLE 1: Graph . Identify the focus, directrix, and
Axis of symmetry.

13. EXAMPLE 2:
Write an equation of a parabola whose vertex lies on the origin, and has a directrix of y=-3/2

14. U-TRY #1:
Graph the equation. Identify the focus, directrix, and axis of symmetry of the parabola.
a) b) c) d)
2) Write the standard form of the equation of the parabola with vertex at (0,0) and the given directrix or focus.
directrix: y= c) directrix: y=4
b) Focus (-2,0) d) focus (0,3)

15. HOMEWORK
Sec 9.2 WS