八年级数学分式 1/x - 1/y =3 求..

把1/x - 1/y=3进行化简变为y-x/xy=3,所以，y-x=3xy,2x+3xy-2y/x-xy-y可变为2（x-y)+3xy/x-y-xy,x-y=-3xy,2.-3xy+3xy/-3xy-xy
所以，-3xy/-4xy=3/4

2x+3xy-2y/x-xy-y 上下同除xy
=(2/y+3-2/x)/(1/y-1-1/x)
=[-2（1/x-1/y）+3]/[-(1/x-1/y-1)]
=-3/(-2)
=3/2

3/4
1/x-1/y=3
所以y-x=3xy
原式=（2x+y-x-2y)/(-xy-3xy)
=(x-y)/(-4xy)
=3/4

答案是3/4，先把一式通分得到X-Y=-3XY ,再带入二式即可求得！

1.5