## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

the polynomial $x^2 + 4x + 16$ is prime.
To factor the second-degree polynomial $x^2 + 4x + 16$, we have to find integers whose product is $16$ and whose sum is $4$. But there are no such factors, so the polynomial $x^2 + 4x + 16$ is prime.