∵b-a/ab=3
∴b-a=3ab

[(3a-1)(3b+1)+1]/[(b-a0+12ab]
=[9ab-3b+3a-1+1]/[(b-a)+12ab]
=[9ab-3(b-a)-1+1]/(3ab+12ab)
=(9ab-9ab)/15ab
=0/15ab
=0