Write an equation of a parabola that opens to the left, has a vertex at the origin, and a focus at (-9, 0.

The standard equation of parabola:

(y-k) ²=4p (x-h), with:

a) vertex = (h, k)

b) focus = (h+p, k)

c) directrix = (x=h-p)

Since this parabola has a vertex at (0,0) that means h=k=0

Hence the equation becomes: y²=4px, let's calculate p:

focus is given (-9,0) Remember h+p = - 9 & since h=0, then p = - 9

===> y² = - 36x