Posted by dylan on .
Find an equation for the parabola that has its vertex at the origin and directrix x=9.
If your answer is in the form x^2=Ay, then input here: A=
if your answer is in the form y^2=Ax, then input here: A= .

precalculus 
Reiny,
using y^2 = 4px , p = 9
so we get y^2 = 36x , placing the focus on the xaxis
comparing this with your y^2 = Ax
would make A = 36