1/(y^2-x^2)和1/(2x-2y)的公分母是(),通分后,1/(y^2-x^2)可化为（）,1/(2x-2y)可化为（）.今晚好的加分

[(-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+y=1 5x-2y=8 3x-y=7 2x-y=3x表示y和用y表示x (x-y)(2x-y-1) (x-2y)(x+y)-2x(-2x-3y)+6x(-x-y),其中x=-1,y=2要讲解和答题 (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 (x+2y-5)^2和（x-2y-1)(x+2y-1)的结果 2y(x+二分之一y)-[(x+y)(x-y)+2y(y+x)],其中|x-1|=2 (2x-2y)/3-(x-y)=-1和6(x+y)-4(2x-y)=16 2x+4y=3 -3x-2y=1 ..求x和y 2x+y=1,25x+2y=-40,求x和y? （x-y)(x+y)-(x+y)^2+2y(y-x),其中x=1,y=3. 解方程组,(x+y)^2-3(x+y)=0和x-y=1 已知X和Y满足3X+4Y=2,X-Y-1/7 解方程组3(x+y)-4(x-y)=4和(x+y)/2+(x-y)/6=1kkkkkkkk x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 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