Evaluate the expression $LaTeX: \displaystyle 4 A + 2 B$
$LaTeX: A = \left[\begin{matrix}-3 & 6\\2 & 5\\6 & -1\end{matrix}\right], \text{ and } \quad\quad B = \left[\begin{matrix}-2 & 7\\-7 & 9\\3 & -5\end{matrix}\right]$

The sum is $LaTeX: \displaystyle \left[\begin{matrix}-16 & 38\\-6 & 38\\30 & -14\end{matrix}\right]$ .