Question

（m+n)^2-9(m-n)^2

Answer 1

（m+n)^2-9(m-n)^2
=[(m+n)+3(m-n)][(m+n)-3(m-n)]
=(4m-2n)(4n-2m)
=4(2m-n)(2n-m)

追问

后面的答案时-4（2m-n)(m-2n)..和您的答案是一个意思吗

追答

一样

追问

(4m-2n)(4n-2m)是怎么到-4（2m-n)(m-2n)的..麻烦您写下步骤行吗

追答

(4m-2n)(4n-2m)
=2×﹙2m-n)×[-2(m-2n)]
=－4(2m-n)(m-2n)

Answer 2

（m+n)^2-9(m-n)^2
=[(m+n)-3(m-n)][(m+n)+3(m-n)]
=(m+n-3m+3n)(m+n+3m-3n)
=(4n-2m)(4m-2n)
=4(2n-m)(2m-n)