Answer
$\begin{bmatrix} 6 &6\\-12&9\end{bmatrix} $.
Work Step by Step
Add the corresponding elements to obtain:
$\begin{bmatrix} 9 & 4\\-8&2\end{bmatrix} +\begin{bmatrix} -3 &2\\-4&7\end{bmatrix} =\begin{bmatrix} 9-3&4+2\\-8-4&2+7\end{bmatrix} =\begin{bmatrix} 6 &6\\-12&9\end{bmatrix} $
Therefore, the sum of two matrices is: $\begin{bmatrix} 6 &6\\-12&9\end{bmatrix}$.
