2x-3y=3,4x-3y=15.求x,y的直（用消元）

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-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) 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:3x-5y=0,求x/y,x-y/y,x-y/x 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 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 x(x-3y)=4y(x-3y),求x:y 已知|x|=2,|y|=3,|x+y|=-(x+y)求x-y (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= y=3(x-y),x=2(x-y)求x,y的值 已知(x+2y)(2x-3y)=y(y-4x),试求x/y的值 x/3=y/4,求(x*x-xy)/(x*x+y*y)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2x-y/x+3y=2,求代数式4x-2y/x+3y减4x+12y除以2x-y