The circle with center (h,k) and radius r has equation (x-h)2 + (y-k)2 = r2.
Since the center is (7,-24), we have (x-7)2 + (y+24)2 = r2.
Since the graph goes through the point (0,0), (-7)2 + 242 = r2, r2 = 625
Equation: (x-7)2 + (y+24)2 = 625.