Question

Find AB using the given matrices.

Answer 1

The entry in row 1, column 1 of
`\mathbf{AB}` is

`\begin{bmatrix}2&4\end{bmatrix}\begin{bmatrix}5\\6\end{bmatrix}=2\cdot5+4\cdot6=34`

(i.e. the dot product of row 1 of
`\mathbf A` and column 1 of
`\mathbf B`)

The entry in row 1, column 2 of
`\mathbf{AB}` is

`\begin{bmatrix}2&4\end{bmatrix}\begin{bmatrix}-9\\-4\end{bmatrix}=2\cdot(-9)+4\cdot(-4)=-34`

The second option is the correct answer.