If n is a positive integer and 2n+2n+1=k,what is 2n+2 in terms of k.
问题描述：
If n is a positive integer and 2n+2n+1=k,what is 2n+2 in terms of k.
答
题目应该是：如果n为正整数,且2^n + 2^(n+1)=k,那么,用k来表示2^(n+2)为多少?
由2^n + 2^(n+1)=k
2^n+2×2^n =k,
3×2^n=k,2^n=k/3,
所以2^(n+2)＝2^2×2^n=4×k/3=4k/3