SOLUTION: What is the directrix of the parabola with equation 36x = 9y2? show work please

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Question 475247: What is the directrix of the parabola with equation 36x = 9y2? show work please
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
The standard form of the parabola is 4c%28x-h%29+=+%28y-k%29%5E2, where (h,k) is the vertex, and c is the directed distance between the focus and the vertex.
==> the vertex is (0,0), the equation is equivalent to 4x+=+y%5E2, and 4c = 4.
==> c = 1.
Since the directrix has the same (absolute) distance as the focus from the vertex, but located on the opposite side of the vertex, the directrix is the (vertical) line x = -1.