1.(x+y)²-4xy=( )²

1.(x+y)²-4xy=( )² 1.已知3x²-xy+y²=10,-xy+4y²=4,则x²-y²的值 3x²-4xy+y² 1.已知x/y=3/4,求(7x²-3xy+2y²)/(2x²-3xy+7y²) 1 3x²+4xy-y²= 1.已知x²--2xy=47 ,3xy+4y²=--19,求代数式3x²+8y² x²+y²+4x-8y+20=0,求分式x²-y²/xy的值 x²+y²+4x-8y+20=0,求(x²-y²)÷xy的解 x²-4y²/x²+2xy+y²÷x+2y/2x²+2xy 已知x²y²+x²+y²=10xy-16 求x,y xy²/(x²y-y) × x²/(x²+x)= xy²/(x²y) - y×x²/(x²+x)=