答：
[xy(x²－3y)＋3xy²]﹙﹣2xy﹚＋x³y²﹙2x－y﹚
=(x³y-3xy²+3xy²)*(-2xy)+2(x^4)y²-x³y³
=-2(x^4)y²+2(x^4)y²-(xy)³
=-(xy)³
=- [(-1/2)*(-5) ]³
=- (5/2)³
=-125/8