9n^2-(m+n)^2
问题描述：
9n^2-(m+n)^2
答
原式=(3n)²-(m+n)²
=[3n+(m+n)][3n-(m+n)]
=(m+4n)(2n-m)
答
9n^2-(m+n)^2
=(3n+m+n)(3n-m-n)
=(4n+m)(2n-m)
答
9n^2-(m+n)^2
=(3n-m-n)(3n+m+n)
=(2n-m)(4n+m)
答
(3n+m+n)(3n-m-n)=(4n+m)(2n-m)
答
根据平方差公式：
原式=（3n+m+n）(3n-m-n)
=(4n+m)(2n-m)