### Home > PC > Chapter 12 > Lesson 12.1.1 > Problem12-12

12-12.

Let $M = \left[ \begin{array} { l l } { 1 } & { 2 } \\ { 3 } & { 0 } \end{array} \right]$ and $N = \left[ \begin{array} { l l } { a } & { 4 } \\ { c } & { d } \end{array} \right]$. In some cases $MN = NM$. Find these conditions.

$MN=\begin{bmatrix}1a+2c&1(4)+2(d)\\3a+0c&3(4)+0d\end{bmatrix}$