Chapter 3 Linear Systems and Matrices - 3.8 Use Inverse Matrices to Solve Linear Systems - 3.8 Exercises - Quiz for Lessons 3.6-3.8 - Page 217: 1

$2AB=\begin{bmatrix} 4 & -14\\ 20& -26 \end{bmatrix}$

$2AB=2.\begin{bmatrix} 1 & -4\\ 5 & 2 \end{bmatrix}.\begin{bmatrix} 2 &3\\ 0 & 1 \end{bmatrix}$ $=2\begin{bmatrix} 2+0 & -3-4\\ 10+0 & -15+2 \end{bmatrix}$ $=2\begin{bmatrix} 2 & -7\\ 10&-13 \end{bmatrix}$ $=\begin{bmatrix} 4 & -14\\ 20& -26 \end{bmatrix}$