挺简单的 1/x-1/y=3 (y-x)/xy=3 y-x=3xy x-y=-3xy 所以(2x+3xy-2y)/(x-2xy-y) =[2(x-y)+3xy]/[(x-y)-2xy] =(-6xy+3xy)/(-3xy-2xy) =-3xy/(-5xy) =3/5