Question

A parabola can be represented by the equation x2 = –20y.

What are the coordinates of the focus of the parabola?

(–5,0)
(5,0)
(0,5)
(0,–5)

Answer 1

Answer:

${x}^{2} = - 20y \\ y = - \frac{1}{20} {x}^{2} \\ { \tt{y = 4a {x}^{2} }} \\ a = - \frac{1}{5} \\ \\ { \tt{focus = (0, \: - 5)}}$