1/x-1/y=2,通分后就是(y-x)/xy=2,所以y-x=2xy,x-y=-2xy
然后再带入到题目中
X-XY-Y/(3X+XY-3Y)=[(X-Y)-XY]/[3(X-Y)+XY]
=[(-2XY)-XY]/[3*(-2XY)+XY]=-3XY/(-5XY)=3/5
1/x-1/y=2,通分后就是(y-x)/xy=2,所以y-x=2xy,x-y=-2xy
然后再带入到题目中
X-XY-Y/(3X+XY-3Y)=[(X-Y)-XY]/[3(X-Y)+XY]
=[(-2XY)-XY]/[3*(-2XY)+XY]=-3XY/(-5XY)=3/5