Answer
$\begin{bmatrix} 4\\ 42 \end{bmatrix}$
Work Step by Step
Since, the dimensions of matrix $A$ is $2 \times 2$ and that of matrix $B$ is $2 \times 1$. Therefore, the number of columns of matrix-$A$ will be same as the number of rows of the matrix-$B$. when we take their product $AB$.
$AB=\begin{bmatrix} -1 & 5\\7& 0 \end{bmatrix} \begin{bmatrix} 6 \\2\end{bmatrix} \\=\begin{bmatrix} (-1)(6)+(5)(2)\\(7)(6)+0 \end{bmatrix}\\=\begin{bmatrix} -6 +10 \\ 42+0 \end{bmatrix}\\=\begin{bmatrix} 4\\ 42 \end{bmatrix}$
