A=2y2+2ky-2y-1
B=-y2+ky-1
3A+6B
=3(2y^2+2ky-2y-1)+6(-y^2+ky-1)
=6y^2+6ky-6y-3-6y^2+6ky-6
=12ky-6y-9
=(12k-6)y-9
3A+6B的值与y无关
所以
12k-6=0
k=1/2
A=2y2+2ky-2y-1
B=-y2+ky-1
3A+6B
=3(2y^2+2ky-2y-1)+6(-y^2+ky-1)
=6y^2+6ky-6y-3-6y^2+6ky-6
=12ky-6y-9
=(12k-6)y-9
3A+6B的值与y无关
所以
12k-6=0
k=1/2