The entry in row 1, column 1 of [tex]\mathbf{AB}[/tex] is
[tex]\begin{bmatrix}2&4\end{bmatrix}\begin{bmatrix}5\\6\end{bmatrix}=2\cdot5+4\cdot6=34[/tex]
(i.e. the dot product of row 1 of [tex]\mathbf A[/tex] and column 1 of [tex]\mathbf B[/tex])
The entry in row 1, column 2 of [tex]\mathbf{AB}[/tex] is
[tex]\begin{bmatrix}2&4\end{bmatrix}\begin{bmatrix}-9\\-4\end{bmatrix}=2\cdot(-9)+4\cdot(-4)=-34[/tex]
The second option is the correct answer.
