where
The sum of the polynomials of these 4 languages is 
We use the inclusion-exclusion principle to determine the polynomial
describing 
The sum of the polynomials of these 6 languages is 
The sum of the polynomials of these 4 languages is 
The polynomial of this language is 
The language 
of words involving at least 3
consecutive Bs is described by the polynomial
using the inclusion-exclusion principle.