-9(m-n)^2+(m+n)^2 怎么算
问题描述：
-9(m-n)^2+(m+n)^2 怎么算
答
(m+n)^2-(3m-3n)^2=(m+n+3m-3n)(m+n-3m+3n)=(4m-2n)(-2m+4n)=4(2m-n)(2n-m)
-9(m-n)^2+(m+n)^2 怎么算
(m+n)^2-(3m-3n)^2=(m+n+3m-3n)(m+n-3m+3n)=(4m-2n)(-2m+4n)=4(2m-n)(2n-m)