Use the fact that (x-h)² + (y-k)² = r² is the equation of a circle, where (h,k) = the center and r = the radius. In your problem, origin = (0,0) and so h=0 and k=0 and radius = r = 7. (x-0)² + (y-0)² = 7² which simplifies to x² + y² = 49 Edwin
