Question

Write the standard form of a parabola with focus at (0,-5) and directrix y=5

Answer 1

This is a vertical parab because the directrix is horiz. It opens down, because the directrix is above the focus. The vertex is (0,0), half way between the focus and the directrix. Thus, p = -5. Let's use this info

4py = x^2

Here, 4(-5)y = x^2, or -20y = x^2, or y = (-1/20)x^2