\begin{itemize}
\item $A+B=\begin{pmatrix}-2+1&0-2&1-1\\1+2&-1+2&0+0\\3+3&0+0&1+1\end{pmatrix}=\begin{pmatrix}
-1&-2&0\\3&1&0\\6&0&2\end{pmatrix}$.

\item $-3A=\begin{pmatrix}-2\times(-3)&0\times(-3)&1\times(-3)\\1\times(-3)&-1\times(-3)&0\times(-3)\\3\times(-3)&0\times(-3)&1\times(-3)\end{pmatrix} = \begin{pmatrix}6&0&-3\\-3&3&0\\-9&0&-3\end{pmatrix}$.

\item $A \times C = \begin{pmatrix}-2\times1+0\times2+1\times0 & -2\times1+0\times0+1\times(-1)\\
1\times1-1\times2+0\times0 & 1\times1-1\times0+0\times(-1)\\
3\times1+0\times2+1\times0 & 3\times1+0\times0+1\times(-1)
 \end{pmatrix}$

 donc $A\times C = \begin{pmatrix}-2 & -3\\-1 & 1\\3 & 2\end{pmatrix}$.

 \item $D \times C = \begin{pmatrix} -1\times1+0\times2+1\times0 & -1\times1+0\times0+1\times(-1) \end{pmatrix}$

 soit $D \times C = \begin{pmatrix}-1 & -2 \end{pmatrix}$.
\end{itemize}
