Answer
$\left[\begin{array}{c}
{3}\\
{-4}\\
{0}\\
{3}\end{array}\right]$
Work Step by Step
If $A$ is an $m\times\boxed{n }$ matrix and $B$ is an $\boxed{n }\times k$ matrix,
then the product $AB$ is the $m\times k$ matrix whose $ij-$th entry is the product
$(AB)_{ij}=[a_{i1}\ a_{i2}\ a_{i3}\ \ldots\ a_{in}]\left[\begin{array}{l}
b_{1j}\\
b_{2j}\\
b_{3j}\\
\vdots\\
b_{nj}
\end{array}\right]$
$=a_{i1}b_{1j}+a_{i2}b_{2j}+a_{i3}b_{3j}+\cdots+a_{in}b_{nj}$.
-------
Here,
A is a $4\times 4$ matrix, B is a $4\times 1$ matrix
AB is defined, and is a $4\times 1$ matrix.
$AB=\left[\begin{array}{c}
{(1+0+2+0)}\\
{(-1-3+0+0)}\\
{(-2+0+2+0)}\\
{(0+3+0+0)}\end{array}\right]$$=\left[\begin{array}{c}
{3}\\
{-4}\\
{0}\\
{3}\end{array}\right]$
