Question

Which is the directrix of a parabola with equation X^2=8y

Answer 1

Alright so, After rewriting the equation in a standard parabola, you get:
4 x 2 (y-0) =(x - 0)^2

Simplify it to get: 
y= 0-p
y= 0-2

When you simplify that, your answer is:
y=-2

There you go folks, just saved you from reading that long paragraph of an answer the other guy has (I don't even think the answer is in there lol, I think he just wanted to help people solve it but still most people come here for answers)