mayflower77
May 5, 2009, 06:53 PM
(x+4)^2=16(y+2) find the vertex, focus, and directix of the parabola. Graph the equation. I got the vertex, how do find the focus and directix.
Perito
May 6, 2009, 05:23 AM
Parabola - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Parabola) gives you a lot of information about parabolas.
Basically, if you arrange the equation for a parabola in this form:
(x-h)^2=4p(y-k)
or
(y-k)^2=4p(x-h)
The vertex is (x,k); the focus is (h, k+p); the directrix is y=k-p where p is the distance from the vertex to the focus.
Is your equation in this form?
(x+4)^2=16(y+2)
If it is, you should be able to pick out the values directly. The + and/or - signs shouldn't throw you. If you had (x+7)^2, h is simply -7.