x²-5xy+6y²=0,
(x-3y)(x-2y)=0
x=3y或x=2y
(1)当x=3y
x+y分之x-y
=(3y-y)/(3y+y)
=1/2
(2)当x=2y
x+y分之x-y
=(2y-y)/(2y+y)
=1/3
所以：x+y分之x-y=1/2或1/3