你好!
数学之美团为你解答
1 +(n-m)/(m+2n) ÷ (m²-n²) / (m²+4mn+4n²)
= 1 + (n-m)/(m+2n) × (m+2n)² / [(m+n)(m-n)]
= 1 - (m+2n)/(m+n)
= [ (m+n)-(m+2n)] / (m+n)
= - n/(m+n)