(4a²-3a)+(2+4a-a²)-(2a²+a-1)
=4a²-3a+2+4a-a²-2a²-a+1
=(4a²-a²-2a²)-(3a-4a+a)+(2+1)
=a²+3
因为a=-2,带入原式=a²+3=(-2)²+3=7