问题描述: 2/1*4+2/4*7+2/7*10+2/10*13+.+2/(3n-2)(3n+1) 1个回答 分类:数学 2014-10-24 问题解答: 我来补答 2/(3n-2)(3n+1)=(2/3)*[1/(3n-2)-1/(3n+1)]所以原式=(2/3)*[1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+.+1/(3n-2)-1/(3n+1)]=(2/3)*[1-1/(3n+2)]=(6n+2)/(9n+6) 展开全文阅读