3xy(x²-xy²+xy)-xy²(2x²-xy+2x)
=3x³y-3x²y³+3x²y²-2x³y²+x²y²-2x²y²
=3x³y-2x³y²-3x²y³+2x²y² (求值)
如果是因式分解:
3xy(x²-xy²+xy)-xy²(2x²-xy+2x)
=3x³y-3x²y³+3x²y²-2x³y²+x²y²-2x²y²
=3x³y-2x³y²-3x²y³+2x²y²
=3xy(x²-y²)-2x²y²(x-1)
=xy[(3(x²-y²)-2xy(x-1)]
=xy(3x²-2x²y-3y²+2xy)