问题描述: 已知xy/x+y=3,求2x-3xy+2y/-x+3xy-y的值 1个回答 分类:数学 2014-11-20 问题解答: 我来补答 xy/x+y=3 即:xy=3(x+y)(2x-3xy+2y)/(-x+3xy-y)=[2(x+y)-3xy]/[3xy-(x+y)]=[2(x+y)-9(x+y)]/[9(x+y)-(x+y)]=-7(x+y)/8(x+y)=-7/8 展开全文阅读