已知x+y=4,|x|+|y|=7,求x-y的值已知x+y=4,|x|+|y|=7,那么x-y的值是

已知：4x = 5y,求(x+y) ：y 已知:3x-5y=0,求x/y,x-y/y,x-y/x 已知（x+y）2 =2,(x-y)3 =3,求(x+y)7(x-y)2(x+y)3(y-x)4 的值 已知实数x.y满足根号(x+y-8)+根号(8-x-y)=根号(3x-y-4)+根号(x-2y+7),求x,y 已知x+y=6,xy=7,试求x*x+y*y,x*x-y*y的值 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y 已知x×x×y×y+x×x+y×y+1=4xy,求x,y的值快 已知7x+5y/2y-x=3/2,且x≠0,求X/x-4y 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 已知5x-4y=0,求x:y和x+y:y的值 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 1、已知x/y=7/2,求x/x+y 2、已知x/2=y/3=z/4,求x+y+z/2x+3y-z!1、已知x/y=7/2,求x/x+y2、已知x/2=y/3=z/4,求x+y+z/2x+3y-z! 已知x=3分之一,y=-2分之一,求代数式x-(x+y)+(x+2Y)-(x+3y)+(x+4y)...-(x+2009y) 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 已知:【(x²+y²)-(x-y)²+2y(x-y)】/4y=1,求4x/4x²-y²-1/2x+y 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙