Answer
The required solution is $\left\{ -\sqrt{3},0,\sqrt{3} \right\}$
Work Step by Step
Let us consider the provided expression:
${{u}^{3}}-3u=0$
Now, take out the common term as given below:
$\begin{align}
& {{u}^{3}}-3u=0 \\
& u\left( {{u}^{2}}-3 \right)=0
\end{align}$
Also, find the possible values of $u$:
$u=0$
And,
$\begin{align}
& {{u}^{2}}-3=0 \\
& {{u}^{2}}=3 \\
& u=\pm \sqrt{3}
\end{align}$
Thus, the possible values are $-\sqrt{3}$, $0$ and $\sqrt{3}$.
