A=2XX+3XY-2X-1,B=-(XX)+XY-1.
3A+6B
=3[2XX+3XY-2X-1]+6[-(XX)+XY-1]
=6XX+9XY-6X-3-6XX+6XY-1
=15XY-6X-4
=3X(5y-2)-4
X的系数是(5y-2)
与X无关,
说明x的系数为0
所以5y-2=0
y=2/5