By definition, a trinomial is an algebraic expression that has 3 terms.
In the given polynomial:
[tex]-4b^4+5m^3+2z[/tex]
We can identify the following terms:
[tex]\begin{gathered} -4b^4\text{ First term} \\ +5m^3\text{ Second term} \\ +2z\text{ Third term} \end{gathered}[/tex]
Then, we can say it is a trinomial.
