Soluzione
a)
$i\neq 1$, $i^{2}=-1$, $i^{3}=-i$ e $i^{4}=1$; quindi $\vert i\vert=4$;
b)
$\left(\begin{array}{ccc}1&2&3\\
2&1&3\end{array}\right)\neq id$, e $\left(\begin{array}{ccc}1&2&3\\ 2&1&3\end{array}\right)^{2}=id$; $\left\vert\left(\begin{array}{ccc}1&2&3\\
2&1&3\end{array}\right)\right\vert=2$;
c)
$\left(\begin{array}{ccc}1&2&3\\
2&3&1\end{array}\right)\neq id$, $\left(\begin{array}{ccc}1&2&3\\
2&3&1 \end{array}\right)^{2}=\left(\begin{array}{ccc}1&2&3\\
3&1&2\end{array}\right)\neq id$, e

\begin{displaymath}\left(\begin{array}{ccc}1&2&3\\
2&3&1\end{array}\right)^{3}=...
...t)
\left(\begin{array}{ccc}1&2&3\\ 2&3&1\end{array}\right)=id;\end{displaymath}

quindi $\left\vert\left(\begin{array}{ccc}1&2&3\\
2&3&1\end{array}\right)\right\vert=3$.







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