Given

$\displaystyle x^2-4x=y+4$

Find the vertex, focus and directrix

So i know that i need to complete the square

$\displaystyle x^2-4x+4=y+4+4$

$\displaystyle (x-2)^2=(y+8)$

Vertex is at $\displaystyle (2,-8)$

and im having a bit of trouble on the focus and directrix....

Thanks