x+2y=2x+y+1=7x-y 求：2x-y?

已知4x=9y求(1)x+y/y (2)y-x/2x 已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) x+y=1,xy=-1/2,求x(x+y)(x-y)-x(x+y)2 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 已知x²+y²+5=2x+4y,求【2x²-(x-y)(x-y)】【(x+y-1)(x-y y=2x*arctan(y/x),求y‘’ 若x、y满足2x+y=6,x-3y=1,求7y(x-3y)²-2(3y-x)³的值 1、x(x-y)(x+y)-x(x+y)^2 已知：3x=8y.求（1）x+y/y (2)2x+3y/x-2y [x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013 若|x+2y-1|+y²+4y+4=0,求（2x-y）²-2（2x-y)(x+2y)+(x+2y)&