The equation will be in the form (x - xc)2 + (y - yc)2 = r2 where (xc, yc) are the coordinates of the centre (in this case xc = -5 and yc = -10) and r is the radius, obtained here from r2 = (-11 - -5)2 + (-9 - -10)2 or r2 = 37, so:
(x + 5)2 + (y + 10)2 = 37
.
