3A+6B
=3(2X^2+3XY-2X-1)+6(-X^2+XY-1)=6x^2+9xy-6x-3-6x^2+6xy-6
=15xy-6x-9
=x(15y-6)-9
与x无关
则x前系数 =0
15y-6=0
y=2/5