arey no three variables..
see the tangent to the parabola at the point 6,9 is also a tangent to the circle.
now, tangent eqn for the para at 6,9 : y-3x+9=0
and centr of circle = (0,1)
now radius of the circle = perpendicular dist of 0,1 from that tangent.
so r=√10.
now u will get eqn.