-14xy-x²-49y² 3x³-12x²y+12xy²

计算：(xy-x²)×x-y/xy [-xy/(x-y)²]²×(y²-xy/x)³ x²/xy-x/y (3xy)² · (x²+xy-y²)-3xy(3x³y+3x²y&# 先化简,再求值:{xy(x²-3y)+3xy²}(-2xy)+x³y²(2x-y x/xy-y²与y/x²-xy 通分 x-y/x²÷x²-2xy+y²/xy*（xy-x²） x²-2xy+y²分之x²+2xy-3y³如何因式分解 计算：（-7x²y）（2x²y-3xy³+xy） 3xy²除以(-x分之6y²)³乘以(x分之12y)² 3x²y+xy²-[2xy²-4x²y+（x²y-2xy²） (2x²y-3xy²)-3(x²y-2xy²)+2（x²y-4xy&#