## Precalculus (6th Edition) Blitzer

$-6$, $(x+6)(2x^2-x-1)=0$
Based on the result of synthetic division with a zero remainder, the polynomial is divisible by $x+6$ and thus $-6$ is a root. The result also gives the quotient $2x^2-x-1$ which means that the equation can be factored as $(x+6)(2x^2-x-1)=0$