What type of polynomial is: - 2/3 x b3

This would be a binomial.

Hello!

Polynomials can be classified two different ways - by the number of terms and by their degree.

A monomial has just one term.

A binomial has two terms.

A trinomial has three terms.

A polynomial has four or more terms, and can also be classified as a monomial, binomial, and trinomial.

Therefore, the polynomial - 2/3 * b³ is classified as a binomial.