1.通分 (m+2n)(n-m)/(n+m)(芹激瞎n-m)+n(n+m)/(n+m)(n-m)-(2m)(n+m)/(n+m)(n-m)=(mn-m²+2n²-2mn+n²铅亮+mn-2mn-2m²)/(n+m)(n-m)=(3n²-3m²-2mn)/(n+m)(n-m)2.(x-y)与y-x是相反数 他们的平方相等∴原式=y/(y-x)²嫌空-x/(y-x)²=(y-x)/(y-x)²=1/(y-x)