若1/x-1/y=3,则分式3x-xy-3y/x+2xy-y的值为

问题描述:

若1/x-1/y=3,则分式3x-xy-3y/x+2xy-y的值为
A:2 B:8/5 C:10 D:-10

是(3x-xy-3y)/(x+2xy-y)的吧?
如果是则 选C
由1 /x -1/ y =3,得y-x=3xy,
∴x-y=-3xy,
∴原式=(3(x-y)-xy)/( (x-y)+2xy) =(-9xy-xy)/( -3xy+2xy) =-10xy /-xy =10
故答案为C.