[(-3xy)².x⁴-2x²(3xy²)².y／2]÷(-3x&#

-3(xy-2x²)-[y²-(5xy-4x²)+2xy] x-y/x²÷x²-2xy+y²/xy*（xy-x²） 已知x:y=3:2,求(x²+3xy)/(xy+2xy) 3x²y+xy²-[2xy²-4x²y+（x²y-2xy²） (2x²y-3xy²)-3(x²y-2xy²)+2（x²y-4xy&# 先化简,再求值:{xy(x²-3y)+3xy²}(-2xy)+x³y²(2x-y 化简4xy-3y²-3x²+xy-3xy-2x²+x²-2y² 已知x/y=3,求(x²+2xy-3xy²)/(x²-xy+y²) 下列多项式:(1)x²+xy-y²;(2)-x²+2xy-y²;(3)xy+x& 3x-2xy-8-2x+6xy-x²+6、-x²+2xy-y²-3x²-2xy+ 计算 2xy[4x²y²-3y（xy+x²y）-xy²] 急![(3x+y)²-3(3x-y)(x+y)-(x-3y)(x+3y)]÷(2xy)