m^2-4mn+3n^2=
问题描述：
m^2-4mn+3n^2=
要用配方方法分解因式
答
m^2-4mn+3n^2
=m^2-4mn+4n^2-n^2
=(m-2n)^2-n^2
=[(m-2n)+n][(m-2n)-n]
=(m-n)(m-3n)