化简：2x²y+{2xy-[3x²y-2(-3x²y+2xy)]-4xy}

化简4xy-3y²-3x²+xy-3xy-2x²+x²-2y² (2x²y-3xy²)-3(x²y-2xy²)+2（x²y-4xy&# 3x²y+xy²-[2xy²-4x²y+（x²y-2xy²） -3(xy-2x²)-[y²-(5xy-4x²)+2xy] 计算 2xy[4x²y²-3y（xy+x²y）-xy²] 先化简,再求值:{xy(x²-3y)+3xy²}(-2xy)+x³y²(2x-y x-y/x²÷x²-2xy+y²/xy*（xy-x²） 化简-3x²y+2x²y+3xy²-2xy² 化简（3X²-XY+Y²）-5(X²-XY+2Y²） -4x²y-8xy²+2x²y-3xy² 已知x:y=3:2,求(x²+3xy)/(xy+2xy) 化简(x²y-4y²)/(x²+4xy+4y²)*[(4xy)/(x-2y)+x