问题描述: 已知1/x=1/y+3,则(5x+xy-5y)/(x-xy-y)的值为( ) 1个回答 分类:数学 2014-11-21 问题解答: 我来补答 1/x-1/y=3(y-x)/xy=3y-x=3xyx-y=-3xy(5x+xy-5y)/(x-xy-y)=[5(x-y)+xy][(x-y)-xy]=(-15xy+xy)/(-3xy-xy)=-14xy/(-4xy)=7/2 展开全文阅读