原式=-(3a²+4ab)-[a²-2(2a+2ab)]
=-3a²-4ab-(a²-4a-4ab)
=-3a²-4ab-a²+4a+4ab
=(-3a²-a²)+(-4ab+4ab)+4a
=-4a²+4a
当a=-2,b=2/13时
原式=-4×(-2)²+4×(-2)
=-4×4-8
=-16-8
=-24