设m=1/5n 设m等于1/5n求 2n/(m+2n)+m/(2n-m)+4mn/(4n²-m²)

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

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)=(-4...