xy/(x+y)=2
x+y=1/2xy
(3x-5xy+3y)/(-x+3xy-y)
=[3(x+y)-5xy]/[-(x+y)+3xy]
=(3/2xy-5xy)/(-1/2xy+3xy)
=(3/2-5)/(3-1/2)
=-7/5
你是不是分子分母写倒了
若是xy 是分母
x+y是分子
(x+y)/xy=2
x+y=2xy
(-x+3xy-y)/(3x-5xy+3y)
=[-(x+y)+3xy]/[3(x+y)-5xy]
=(-2xy+3xy)/(6xy-5xy)
=xy/(xy)
=1