Question

which expression is a monomial?
$3x^{-2}$
$\frac{1}{x}$
$7$
$x + 1$

Explanation:

A monomial is a single term that is a product of constants, variables, and non-negative integer exponents. Let's analyze each option:

1. $3x^{-2}$ has a negative exponent, so it is not a monomial.
2. $\frac{1}{x}$ is equivalent to $x^{-1}$, which has a negative exponent, so it is not a monomial.
3. $7$ is a constant term, which qualifies as a monomial (a monomial can be a single constant).
4. $x+1$ has two terms, so it is a binomial, not a monomial.

Answer:

7