问题描述： 5*9分之1+9*13分之1+13*17分之1+……+101*105分之1=? 1个回答 分类：数学 2014-12-15 问题解答： 我来补答 1/(5*9)+1/(9*13)+...+1/(101*105)=(1/4)*(1/5-1/9)+(1/4)*(1/9-1/13)+...+(1/4)*(1/101-1/105)=(1/4)*(1/5)-(1/4)*(1/9)+(1/4)*(1/9)-(1/9)*(1/13)+...+(1/4)*(1/101)-(1/4)*(1/105)=(1/4)*(1/5)-(1/4)*(1/105)=(1/4)*(1/5-1/105)=(1/4)*(20/105)=1/21 展开全文阅读
