Sketching Polynomial Functions

To determine whether the given expression is a polynomial, recall that a polynomial is the sum of two or more monomials. A monomial is either a number, a variable, or an expression that is the product of one or more variables. Additionally, monomials can only have non-negative integer exponents. Consider the given expression. $$\begin{array}{c}f(x)=2x^3+3x-\frac{4}{x}+7x^5-1\end{array}$$ Since monomials cannot contain variables in the denominator, the third term in the above expression is not a monomial. Therefore, the given expression is not a polynomial.