Square of the length of the greatest common tangent to the circles given by x2+y2−4=0 and x2+y2−12x+27=0 is ____.

For circle,k2+y2−4=0, centre is C1(0,0)and radius is r1=2.For circle, x2+y2−12x+27=0, centre is C2(6,0)and radius is r2=3.Length of greatest common tangent =C1C22−r1−r22=36−1=35