
Parabola question
Given
$\displaystyle x^24x=y+4$
Find the vertex, focus and directrix
So i know that i need to complete the square
$\displaystyle x^24x+4=y+4+4$
$\displaystyle (x2)^2=(y+8)$
Vertex is at $\displaystyle (2,8)$
and im having a bit of trouble on the focus and directrix....
Thanks

okay i figured it out...
$\displaystyle (x2)^2=a(y+8)$
Since $\displaystyle (y+8)$ doesn't factor, then
$\displaystyle a=1$
general form is $\displaystyle x^2=4ay$
set $\displaystyle 4a=1 => a=1/4$
directrix @ $\displaystyle y=8.25$
focus @ $\displaystyle (2,7.75)$
(Rock) gotta love when posting on here rings a bell.