Practice!

Sample Problem

Given , find the focus and the directrix:

Focus: ( , 0)

Directrix: x =

Solution

Parabola with horizontal axis: (y – k)2 = 4p(x – h), p ≠ 0

Focus is  (h + p, k), Directrix is the line  x = h – p.

From the given equation x=-1/8 y2

-8x = y

4(-2)x = yy

p = -2

Focus: (-2 , 0)

Directrix: x = -p

x = 2