Posted by Marie on .
write the equations of the parabola, the directrix, and the axis of symmetry.
if someone could explain how to do this problem then that would be great! thanks in advance!
Formats to help you find the equation for a parabola:
(x - h)^2 = 4p(y - k)
Vertex = (h, k)
Focus = (h, k + p)
Directrix: y = k - p
You are given the vertex (-4,2) and the focus (-4,6).
Since we know k, which is 2, we can figure out p. Format = (h, k + p) for focus. Therefore, p = 4.
I'll set this up and let you take it from there:
[x - (-4)]^2 = 4(4)(y - 2)
The axis of symmetry is: x = -4 (vertex x-value).
I hope this will help.
good post. mathguru, if you would like to join us here at jiskha as a volunteer teacher, email me at
it did. thanks so much!
Thanks Bob! Just happy to help. :)
Pre Cal -