【(1)/(x-y)+(1)/(x-y)】÷(2x)/(x²-2xy+y²)1-【a-（1）/（1-a）】÷(a²-a+1)/(a²-2a+1)

(x+y)(x-y)+4(y-1) [(-x-y)(-x+y)-(x+y)^2-x(y-y^2)}÷1/2y y'/y=1/x 计算：(1+ y/x-y )·(1- x/x+y) 感激不尽1.x,y满足(x-y-1)(x+y) (1-y+x/y)除以y平方-x平方/x 证明:(y/x)+(x/y)+xy≥x+y+1 x+y分之1-(x+y)的平方x-y 1、y-x/x²-y²2、(x-y)(y-z)(z-x)/(z-y)(y-x)(x-z) 1/(x-y)/(1/y-/x) 因式分解：（1+x+y)(1-x-y) (x+5y)(x-7y-1) （x+y)²-4(x+y-1) (x-y)(2x-y-1) （x+y)(x+y-1)-12因式分解 因式分解:(x+y)-4(x+y-1) y'-(1/x)y=xe^-x (x/x+y-x/y-x-2xy/x.x-y.y)/(1/x-1/y) 分式化简