2x+y/2=5x+2y/4=1,求x+2y+1/2x-3y+7

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x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知4x=9y求(1)x+y/y (2)y-x/2x 已知x²+y²+5=2x+4y,求【2x²-(x-y)(x-y)】【(x+y-1)(x-y 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y 已知x²+y²+5=2x+4y,求代数式（2x²-（x+y)(x-y))x((x+y-1) 已知：3x=8y.求（1）x+y/y (2)2x+3y/x-2y 若x、y满足2x+y=6,x-3y=1,求7y(x-3y)²-2(3y-x)³的值 若|x+2y-1|+y²+4y+4=0,求（2x-y）²-2（2x-y)(x+2y)+(x+2y)&