hi I'm having trouble determining the equation of the parabola where the focus and directrix are given.For example:
focus:(0,0);directrix:y=4

The parabola has equation

(x-h)^{2}=-4p(y-k)

where V(h,k) are the coordinates of the vertex.

p is the distance from the vertex to the directrix and from the focus to the vertex.

Since the vertex is halfway between the directrix and focus,
p=2 and V(0,2)

Sub in the given info and find the equation.