关键在于(2ab^3-a^2b^3-1)^4
a=2
所以(2ab^3-a^2b^3-1)^4=(a^2b^3-a^2b^3-1)^4=1
原式=3a^2b+3ab=a^2b^2+ab^2=ab^2(a+1)=ab^3=2*27=54