分解因式m^2+2m-6n-9n^2=
问题描述：
分解因式m^2+2m-6n-9n^2=
答
m^2+2m-6n-9n^2
=m^2-9n^2+2m-6n
=(m+3n)(m-3n)+2(m-3n)
=(m-3n)(m+3n+2)