(1/x-y+1/x+y)÷xy/x^2-y^22.2x-6/x-2÷x-3/x^2-4x+4 3.(1/b-1/a)乘ab/a^2-b^2

x²/xy-x/y 3x/4x+y - x-2y/4x+y (1-y/y+x)÷x/y²-x² xy-1+x-y [(x+y)^2-(x-y)^2]÷(1/2xy) .(x+y-2)(x+y-2xy)+(xy-1)^2 【(1)/(x-y)+(1)/(x+y)】÷(2x)/(x²-2xy+y²) (x²-4y²)÷(2x+y)/xy×1/x(2y-x）(2x+y)/xy 1/x(2y-x） 都是一项 (x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) 计算x²-x/x²×x/1-x和x²-4y²/x²+2xy+y²÷x+2y/x²+xy 1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y) (x/x+y-x/y-x-2xy/x.x-y.y)/(1/x-1/y) 分式化简 化简求值x-4y/2x-7xy+3y×x-2xy-3y/2x+3xy-2y÷3x-6y/4x-4xy+y,其中：x=1999,y=-1 已知x(x-1)-(x²-y)=-3,求(x²y+xy²)÷xy-2y {(x-y/x^2-2xy+y^2)-(xy+y^2/x^2-y^2)}*(xy/y-1) 证明:(y/x)+(x/y)+xy≥x+y+1 x-y/x^2+xy除以xy-x^2/x^2y^2-x^4*1/x-y 先化简,再求值(x-y/x+y)^2÷(y-x/x^2+2xy+y^2)^2*1/x+y,其中x=-4,y=1 先化简再求值:(x+y)(x-y)+(x^2-2xy+y^2)-(x^2y)^3÷(x^2y)^2,其中x=1,y=2. (x+y)(x-y)+(x-y)^2-(6x^2×y÷2y-2xy^2÷2y)其中x=-3,y=1/3