2AB²-C
=2(2x²+3xy-y²)*(x²y²/4)-(x³y³/8-x²y^7/4)
=x^4y²+3x³y³/2-x²y^4/2-x³y³/8+x²y^7/4
=x^4y²+11x³y³/8-x²y^4/4x³y³/8-x²y^7/4？？哦，对不起，打错了 2AB²-C =2(2x²+3xy-y²)*(x²y²/4)-(x³y³/8-x²y^4/4) =x^4y²+3x³y³/2-x²y^4/2-x³y³/8+x²y^4/4 =x^4y²+11x³y³/8-x²y^4/4