1/x（y-x),1/2x-2y 怎样通分

[(-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/x+y-x/y-x-2xy/x.x-y.y)/(1/x-1/y) 分式化简 (x-y)(2x-y-1) x²/xy-x/y 3x/4x+y - x-2y/4x+y (1-y/y+x)÷x/y²-x² y=x^x的导函数是：y'=x^x(Inx+1)我知道怎样求.但为什么不可以这样求.y=x^x=x*x*x*x*x*x*...*x(x个x) 则y'=(x')*x^(x-1)+x*(x')*x^(x-2)+.=x^x 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 1/x（y-x),1/2x-2y 怎样通分 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. 化简 3x(x^2-x-1)-(x+1)(3x^-x) X^3(x-y)+x(y-x) 化简(2x+y)(2x-y)-(x+2y)(x-2y-1) 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 25(x-y)*2+10(y-x)+125（x-y)^2+10(y-x)+1 二元一次方程 ：2(x+y)-(x-y)=3 (x+y)-2(x-y)=1