(b)
$\left| \begin{matrix}
x + \omega^{2} & \omega & 1 \\
\omega & \omega^{2} & 1 + x \\
1 & x + \omega & \omega^{2}
\end{matrix} \right| = 0$
Applying $C_{1} \rightarrow C_{1} + C_{2} + C_{3}$
$\left| \begin{matrix}
x & \omega & 1 \\
x & \omega^{2} & 1 + x \\
x & x + \omega & \omega^{2}
\end{matrix} \right| = 0\ \ \ \ \ \ \left( \therefore 1 + \omega + \omega^{2} = 0 \right)$
$\Rightarrow \ \ \ x = 0\$is one of the values of $x$ which satisfy the above determinant equation.