因式分解一题.9(m+n)^2-4(m-n)^2

问题描述:

因式分解一题.
9(m+n)^2-4(m-n)^2

[3(m+n)]^2-[2(m-n)]^2=(3m+3n+2m-2n)(3m+3n-2m+2n)=(5m+n)(m+5n)

=(3m+3n-2m+2n)(3m+3n+2m-2n)
=(m+5n)(5m-n)