#### Answer

NOT a polynomial

#### Work Step by Step

$\bf{\text{Solution Outline:}}$
Use the description of a polynomial expression to evaluate if the given expression, $
5x^2 +\dfrac{6}{x}-12
,$ is a polynomial or not.
$\bf{\text{Solution Details:}}$
A polynomial expression is an expression where the exponent of the variable in every term is a nonnegative integer.
The term $\dfrac{6}{x}$ is equivalent to $6x^{-1}.$ So it has an exponent that is NOT a nonnegative integer. Hence, the given expression is $\text{
NOT a polynomial
.}$