∵|a+b+2|与（2ab-1)²互为相反数
∴|a+b+2|+(2ab-1)²=0
∴a+b+2=0,2ab-1=0
∴a+b=-2,ab=1/2
∴(a+b)²=4,3ab=3/2,a+b+1=-1
∴（a+b)²/3ab-3ab/(a+b+1)
=4/(3/2)-(3/2)/(-1)
=8/3+3/2
=16/6+9/6
=25/6
=4又1/6