How do I find the directrix of the parabola whose equation is y=x^2/32?

1 Answer
seph
Oct 19, 2014

You have a parabola with vertex at (0, 0) that is opening upward.

That means your directrix is horizontal.

To get the directrix, transfer x^2's coefficient to the other side.
Equate the resulting coefficient of y to 4d, where d is the distance from the vertex to the directrix

y = x^2/32
=> 32y = x^2

4d = 32
=> d = 8

Since the parabola is opening upward, the directrix is below the vertex.

y = h - d

y = 0 - 8

y = -8

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