1.已知4x^2-3y^2=7,3x^2+3y^2=19,求代数式14x^2-2y^2的值.2.已知xy+x=-1,xy-y=-2,求代数式-x-[2y-2(xy+x)^2+3x]+2[x+xy-y)]^2的值.

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和Y满足3X+4Y=2,X-Y-1/7 已知7x+5y/2y-x=3/2,且x≠0,求X/x-4y 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y 1.已知:x-2y=3,求[(3x+2y)(3x-2y)-(x+2y)(5x-2y)]除4x 的值 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 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) 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：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 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 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 已知:3(x-y)的平方-5x-2=2x-7y-4,求x-y的值 已知(x+2y)(2x-3y)=y(y-4x),试求x/y的值 已知|x|=2,|y|=3,|x+y|=-(x+y)求x-y 已知x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² 已知X=2,求代数式,（2X-Y)(2X+Y)+(2X-Y)(Y-4X)+2X(Y-3X)