(m-n)*(3m-2n+1)=?

问题描述:

(m-n)*(3m-2n+1)=?

3m^2+2n^2-5mn+m-n

原式=m(3m-2n+1)-n(3m-2n+1)
=3m²-2mn+m-3mn+2n²-n
=3m²-5mn+2n²+m-n