问题描述: 设m=1/5n 设m等于1/5n求 2n/(m+2n)+m/(2n-m)+4mn/(4n²-m²)先化简 再求值 1个回答 分类:数学 2014-10-16 问题解答: 我来补答 />原式=2n/(m+2n)-m/(m-2n)-4mn/(m²-4n²)=2n/(m+2n)-m/(m-2n)-4mn/(m²-4n²)=[2n(m-2n)-m(m+2n)-4mn]/(m²-4n²)=(2mn-4n²-m²-2mn-4mn)/(m²-4n²)=(-4n²-m²-4mn)/(m²-4n²)=-(m+2n)²/[(m+2n)(m-2n)]=-(m+2n)/(m-2n)m=1/5n,则n=5m,于是原式=-(m+10m)/(m-10m)=-11m/(-9m)=11/9 答题不易,谢谢 展开全文阅读