Hi, I've recently just learned about Quadratic Function. On my previous homework there was a question which asked me to write in standard form the equation of a parabola. The given information was...

Focus (-2, 0); directrix x = 4

I didn't and still don't understand how to solve this problem. I think I'm supposed to use the standard form of equation for a parabola,

y = a(x - h)^2+k, but I'm not quite sure how I should go about doing it. Can someone please explain this to me? Thank you.