1/y - x ,1/2x - 2y

[(-x-y)(-x+y)-(x+y)^2-x(y-y^2)}÷1/2y 1、y-x/x²-y²2、(x-y)(y-z)(z-x)/(z-y)(y-x)(x-z) (x-y)(2x-y-1) (x/x+y-x/y-x-2xy/x.x-y.y)/(1/x-1/y) 分式化简 x²/xy-x/y 3x/4x+y - x-2y/4x+y (1-y/y+x)÷x/y²-x² 2y(x+二分之一y)-[(x+y)(x-y)+2y(y+x)],其中|x-1|=2 （x-y)(x+y)-(x+y)^2+2y(y-x),其中x=1,y=3. 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 [(-2x-y)^2-(2x+y)(2x-y)]÷2y-1/2y 求(1+y)-2x(1+y)+x(1-y) (x-y/1-x+y/1)÷2y/y-x计算错了，是(1/x-y-1/x+y)÷2y/y-x 化简(2x+y)(2x-y)-(x+2y)(x-2y-1) 把4（x-y+1)+y(y-2x)因式分解 y(y+2)+4x(x-y-1)因式分解是多少 x+2y=2x+y+1=7x-y 求：2x-y? 设x,y满足约束条件x+y>=1,x-y>=-1,2x-y 设x,y满足约束条件x+y>=1,x-y>=-1,2x-y