Let z1 and z2 be two complex numbers satisfying z1=9 and z2-3-4i=4 . Then the minimum value of z1-z2 is

z1=9,z2-3-4i=4z1 lies on a circle with centre C1(0,0) and radius r1=9z2 lies on a circle with centre C2(3,4) and radius r2=4 So, minimum value of z1-z2 is zero at point of contact