2^80=(2^40)^2
2^100=(2^50)^2
2^n=[2^(n/2)]^2
(2^40+2^50)^2
=(2^40)^2+2×(2^40)×(2^50)+(2^50)^2
=2^80+2^91+2^100
n=91
(2^(n/2)+2^40)^2
=[2^(n/2)]^2+2×[2^(n/2)]×2^40+(2^40)^2
=2^n+2^(41+(n/2))+2^80
由此得41+(n/2)=100,解得n=118
(2^(n/2)+2^50)^2
=[2^(n/2)]^2+2×[2^(n/2)]×2^50+(2^50)^2
=2^n+2^(51+(n/2))+2^100
由此得51+(n/2)=80,解得n=58
n可以取三个值,91,118,58