Question

n为自然数,2的n次方减2的负n次方=6,求4的n次方加4的负n次方

Answer 1

2的n次方减2的负n次方=6,

2^n-2^(-n)=6

[2^n-2^(-n)]^2=36

2^2n-2*2^n*2^(-n)+2^(-2n)=36

2^2n-2+2^(-2n)=36

2^2n+2^(-2n)=38

4^n+4^(-n)=38