## Algebra 2 (1st Edition)

$\begin{bmatrix} -26&-22\\ -54&-13 \end{bmatrix}$
If the dimensions of matrix A are $a\times b$ and the dimensions of matrix C are $c\times d$, then AC is defined if $b=c$, and then AC has dimensions $a\times d.$ Hence here: $AC=\begin{bmatrix} 1\cdot-6+(-2)\cdot10&1\cdot8+(-2)\cdot15\\ 4\cdot-6+(-3)\cdot10&4\cdot8+(-3)\cdot15 \end{bmatrix} =\begin{bmatrix} -26&-22\\ -54&-13 \end{bmatrix}$