x^2+y^2=36 is a circle. How can you tell without actually plotting? Where is the center?

Answer 1

The center placed in the point (0,0)

radius = sqrt ( 36 ) = 6

Answer 2

ya gotta know that

(x-h)^2 + (y-k)^2 = r^2

is the equation for a circle of radius r with center at (h,k)