Let (h,k) be the centre of the circle. Then k=h−1 . Therefore, the equation of the circle is given by (x−h)2+[y−(h−1)]2=9… . (1) Given that the circle passes through the point (7,3) and hence we get (7−h)2+(3−(h−1))2=9(7−h)2+(4−h)2=9h2−11h+28=0which gives(h−7)(h−4)=0⇒h=4 or h=7 Therefore, the required equations of the circles are x2+y2−8x−6y+16=0 or, x2+y2−14x−12y+76=0