(m-n)/(2m+2n)-(m的平方+n的平方)/(m的平方-n的方） 等于?

(m-n)/(2m+2n)-(m²+n²)/(m²-n²)=(m-n)/[2(m+n)]-(m²+n²)/[(m+n)(m-n)]=[(m-n)²-2(m²+n²)]/[2(m+n)(m-n)]=(m²-2mn+n²-2m²-2n²)/[2(m+n)(m-n)]=-(m²+2mn+n²)/[2(m+n)(m-n)]=-(m+n)²/[2(m+n)(m-n)]=-(m+n)/[2(m-n)]