2A+3B
=2(-x2-2mx+3x+1)+3(2x2+mx-1)
=-2x²-4mx+6x+2+6x²+3mx-3
=4x²-mx+6x-1
=4x²+(6-m)x-1
∵值与x无关
∴6-m=0
∴m=6