Question

What is the equation of the parabola with a directrix at y = -4 and focus (0, 4).

Answer 1

(x-0)^2 + 3^2- (-1)^2 =2(3+1)

Answer 2

well the standard form I use is

(x -h)^2 = 4a(y - k)

(h, k) is the focus and a is the focal length.

start by finding the value of the focal length a.

the distance between the focus and directrix is 2a