Answer
$-2$ is a solution.
Work Step by Step
The given expression is
$=2x^3-x^2-8x+4$
The value of $c$ is $-2$
Use synthetic division
$\begin{matrix}
-2) &2&-1&-8&4 \\
& &-4&+10&-4 \\
& --&--&--& --\\
& 2&-5&2&0
\end{matrix}$
The remainder is zero.
Hence, the given solution is correct.
