已知A=2x的平方+3xy-2x-1,B=-x的平方+xy-1,若3A+6b的值与x无关,试求y的值.

A=2X^2+3XY-2X-1,B=-(X^2)+XY-1.
3A+6B
=3[2X^2+3XY-2X-1]+6[-(X^2)+XY-1]
=6X^2+9XY-6X-3-6X^2+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