3x^2+2xy
=x(3x+2y)=0
得x=0 或3x=-2y
(1)x=0 y=0
(2) 3x=-2y x=-2y/3
4y^2/9 -2y^2/3 -6y^2
=0
得y=0 x=0
所以x=0 y=0