# Chapter 5 - Section 5.4 - Factoring Trinomials - Exercise Set - Page 361: 21

Prime

#### Work Step by Step

The leading coefficient is 1. If the trinomial can be factored, there must be factors of the constant term whose sum is equal to the coefficient of the middle term. The possible factors of $7$ are: $7(1)$ and $-7(-1)$ Both pairs of factors do not have a sum of $-1$. Thus, the given trinomial is prime.

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