Check below, please.
1) By definition, a Polynomial is defined as an algebraic expression that follows this Pattern:
![P(x)=a_nx^n+a_(n-1)x^(n-1)+.\ldots a_2x^2+\cdots a_0](https://img.qammunity.org/2023/formulas/mathematics/college/jmddav0zmlg190rzl9tdasj9lle4e3amzo.png)
In which, n ∈ N (Natural set) and x ∈ C (Complex Set)
2) Based on that, we can discern the following expressions and classify them this way:
![\begin{gathered} (x^2)/(7)+1\: \: \: \: This\: is\: a\: Polynomial \\ -2x^3+2x+4\quad \: \: \: This\: is\: a\: Polynomial \\ x^(-3)+4x\: \: \: This\: is\: NOT\: a\: Polynomial \\ 6x-x^3+4x\: \quad \: \: \: This\: is\: a\: Polynomial \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/gbx5jxrszr8kma6sbulwq9d6jec78o0mi0.png)
Note that the exponents must be natural numbers