1.
Let z1z_1 and z2z_2 be two complex numbers satisfying ∣z1∣=9|z_1| = 9 and ∣z2−3−4i∣=4|z_2 - 3 - 4i| = 4. Then the minimum value of ∣z1−z2∣|z_1 - z_2| is: