If the point m is on the circle C1: x2 + y2 = 1 and the point n is on the circle C2: x2 + y2-6x-8y + 21 = 0, then the value range of Mn is 0

If the point m is on the circle C1: x2 + y2 = 1 and the point n is on the circle C2: x2 + y2-6x-8y + 21 = 0, then the value range of Mn is 0

The radius of circle C1: x2 + y2 = 1 is 1, the center is (0,0) circle C2: x2 + y2-6x-8y + 21 = (x-3) &# 178; + (y-4) &# 178; - 4 = 0, that is: (x-3) &# 178; + (y-4) &# 178; = 4, the radius is: 2, the center is (3,4) because the center distance of two circles is: √ (3 & # 178; + 4 & # 178;) = 5 > R1 + R2 = 1