Find the vertex focus and the directrix of the parabola give
Find the vertex, focus and the directrix of the parabola given by y^2 -8y - 8x = - 40. Graph the equation.
Solution
y2-8y-8x=-40
we have to use completing the square method here
y2-8y+16 -16-8x=-40
(y-4)2=8x -40 +16
(y-4)2= 8x -24
8x= (y-4)2+24
x=(1/8)(y-4)2+3
comparing it with equation of parabola which is
x= a(y-k)2+h
we get vertex=(3,4)
1/(4p)=1/8
p=2
focus= (h+p,k)=(3+2,4)=(5,4)
directrix , x=h-p
x= 3-2=1
x=1
