化简2/(1/X+1/Y)

化简(2x+y)(2x-y)-(x+2y)(x-2y-1) 2x分之1- x+y分之1(2x分之x+y -x-y)化简 化简1/2x-1/x+y（x+y/2x-x-y） 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 1/(x-y)+1/(x+y)+2x/(x^2+y^2)+4x^3/(x^4+y^4)化简 化简：[(2x-y)平方+（2x+y)(2x-y)-4x(x-y+1)]÷2x 化简 3x(x^2-x-1)-(x+1)(3x^-x) X^3(x-y)+x(y-x) [(-x-y)(-x+y)-(x+y)^2-x(y-y^2)}÷1/2y 化简,求值：[(x/y)-(y/x)]除以[(x/y)+(y/x)-2]除以[1+(y/x)],其中x=1/2,y=1/3 化简：(x-y)/(2x+1) * [(2x+1)/(x+y) - (2xy+y)/(y方－x方)]+y/(x+y) 若x-y=1 化简（x+y)(x^2+y^2)(x^4+y^4)(x^8+y^8)(x^16+y^16) 化简(x+y)+(x+1×2分之一y) [(2x+y)^2-(2x-y)(2x+y)]÷2y-1/2y 化简 化简：(1)(x+1)^2-x(x^2+x-1)-(x^2+1)^0(2)(y-2)(y^2-6y-9)-y(y^2-2y-15) 化简：y=|x-1|+|x+2| 化简【(x+y)^2-2(x-y)^2+(x+2y)(x-2y)】÷y,其中x=2,y=-1 1、y-x/x²-y²2、(x-y)(y-z)(z-x)/(z-y)(y-x)(x-z) 把(x-y)看作一个整体,化简:(1)5(x-y)+2(x-y)-4(x-y);(2)3(x-y²-4(x-y)+7（x-y)-6(x-y)