use these facts to find the equation for the circle

center (0,0), radius=6

a)x2-y2=36
b)x2+y2=36
c)x2-y2=6
d)x2+y2=6

The general form for a circle of radius r, at (a,b) is

(x-a)^2 + (y-b)^2 = r^2