(x+3y)(x-y)-(x+y)^2 =x²-xy+3xy-3y²-x²-y²

急![(3x+y)²-3(3x-y)(x+y)-(x-3y)(x+3y)]÷(2xy) 计算3x[xy-2x(1/y-x/3]+3y(x²-y²) x²/xy-x/y (x+3y)(x-y)-(x+y)^2 =x²-xy+3xy-3y²-x²-y² 2x²-3xy=y²=0（x,y不得o）求x/y+y/x (x-y)²-(3x-3xy+y²)因式分解 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 已知x+y=4.x-y=6.求代数式xy(y²+y)-y²(xy+2x)-3xy的值 若x=1/2,y=1 求x(x²+xy+y²)-y(x²+xy+y²)+3xy( 已知x/y=3,求x²+2xy-3y²/x²-xy+y²