∵(a+2)²+lb+5l=0∴a+2=0 且 b+5=0∴a=-2,b=-5,3a²b-[2a²b-(2ab-a²b)-4a²]-ab=3a²b-2a²b+(2ab-a²b)+4a²-ab=3a²b-2a²b+2ab-a²b+4a²-ab=ab+4a²...