问题描述: 若Sn=n乘(n+2),怎么才能证明1/S1+2/S2+3/S3+…+1/Sn 1个回答 分类:数学 2014-10-01 问题解答: 我来补答 1/Sn=1/[n(n+2)]=[1/n-1/(n+2)]/21/S1+1/S2+…+1/Sn=[(1-1/3)+(1/2-1/4)+(1/3-1/5)+...+1/(n-1)-1/(n+1)+1/n-1/(n+2)]/2=[1+1/2-1/(n+1)-1/(n+2)]/2=3/4-[1/(n+1)+1/(n+2)]/2所以1/S1+1/S2+…+1/Sn 展开全文阅读