Final answer:
The expression -2x - 1 - x + 7 is a polynomial because it contains more than two terms.
Step-by-step explanation:
The expression -2x - 1 - x + 7 is a polynomial because it contains more than two terms. A polynomial is an algebraic expression with one or more terms, which are separated by addition or subtraction.
In this expression, we have four terms: -2x, -1, -x, and 7. Therefore, it is a polynomial.