(-5m+2)-5(2mn-n)
=-5m+2-10mn+5n
=-5(m-n)-10mn+2
=-5*(-3)-10*2+2
=15-20+2
=-3-5（m-n）怎么来的呢？=-5m+2-10mn+5n
=(-5m+5n)+2-10mn
=-5(m-n)+2-10mnthank you！！不客气，希望能帮到你