6X^2 - XY - 2Y^2 = 0
(2x+y)(3x-2y)=0
x=-y/2,或x=2y/3
当x=-y/2时：
(x+y)/y=(-y/2+y)/y=1/2
当x=2y/3时：
(x+y)/y=(2y/3+y)/y=5/3