Question

Given the following matrices, find 3A - 2B. (Hint: find 3A and 2B first and then subtract.)

Answer 1

$A= \left[\begin{array}{cc}1&3\\5&2\end{array}\right] \\ \\3A=\left[\begin{array}{cc}3&9\\15&6\end{array}\right] \\ \\B= \left[\begin{array}{cc}4&9\\0&3\end{array}\right] \\ \\2B= \left[\begin{array}{cc}8&18\\0&6\end{array}\right] \\ \\3A-2B=\left[\begin{array}{cc}3&9\\15&6\end{array}\right]- \left[\begin{array}{cc}8&18\\0&6\end{array}\right]=\left[\begin{array}{cc}3-8&9-18\\15-0&6-6\end{array}\right]= \\ \\=\left[\begin{array}{cc}-5&-9\\15&0\end{array}\right]$