Write an equation of a parabola with a vertex at the origin and a directx at y=5

Directrix at y=5 (horizontal line) → The parabola is vertical

Vertex at the orgin: V = (0,0) = (h, k) →h=0, k=0

The directix is above the vertex→the parabola opens downward→p is negative

p is the distance between the vertex and the directrix→p=-5

Equation has the form:

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

(x-0) ^2=4 (-5) (y-0)

x^2=-20y