最右边是 =31/(n+1)

最右边是 =31/(n+1)
最右边是 
=31/(n+1)

最右边是 =31/(n+1)
1.c(n,k)/(k+1)=n!/[(k+1)!(n-k)!]=[1/(n+1)]c(n+1,k+1)
2.将根据上面关系代入到等式左面=（2^(n+1)-1)/(n+1)=31/(n+1)
3.得2^(n+1)-1=31 n=4