xy^2-3y/xy+y^2=(xy-3)/(x+y)=3/5
5(xy-3)=3(x+y)
x=3(5+y)/(5y-3)
所以,x是3的倍数
x=3时,3=(15+3y)/(5y-3),y=2
所以,x,y的最小值分别为：x=3,y=2