SOLUTION: A Laboratory designed a radio telescope with a diameter of 360 feet and a maximum depth of 40 feet. The graph depicts a cross section of this telescope. Find the equation of this p

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Question 638748: A Laboratory designed a radio telescope with a diameter of 360 feet and a maximum depth of 40 feet. The graph depicts a cross section of this telescope. Find the equation of this parabola.
(in y=ax^2 form.)
There's a picture but i can't take a picture of it, but there's what looks like two y intercepts of (-180,40) and (180,40), with a vertex of (0,0).
What I did was 40=a(180)^2
40=32400a
a=40/32400
a=1/810^2 as my final answer but I'm told this is wrong so I'm stuck....
Answer by solver91311(24713) (Show Source):
You can put this solution on YOUR website!

A quadratic polynomial function of the form has a graph that is a parabola. Any point on the parabola has coordinates

Therefore if is a point on the parabola, then

likewise

and

Hence:

Solve the 3X3 system for and substitute into

John

My calculator said it, I believe it, that settles it