5x+xy-5y/x+2y-y?应该是：(5x+xy-5y)/(x+2xy-y) 吧!解析：已知x分之1 - y分之1=3,那么：(xy)分之(y-x)=3即y-x=3xy所以：(5x+xy-5y)/(x+2xy-y)=[5(x-y)+xy]/(x-y+2xy)=(-15xy+xy)/(-3xy+2xy)=(-14xy)/(-xy)=14/1 （注...