问题描述: 已知m^2+n^2=5,试求代数式(5+2m^2+3n^2-mn)-(4m^2+5n^2-mn)的值 1个回答 分类:数学 2014-12-08 问题解答: 我来补答 (5+2m^2+3n^2-mn)-(4m^2+5n^2-mn)=5-2(m^2+n^2)=5-2*5=-5 展开全文阅读