Answer
Dimension: $2\times 1.$
$A$ is a column matrix.
Work Step by Step
The dimension of $A$ is expressed as m$\times$n,
where m = number of rows, n= number of columns.
$A$ is a square matrix if m=n.
$A$ is a row matrix if m=1
$A$ is a column matrix if n=1
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Here, A has $2$ rows and $1$ columns.
Dimension: $2\times 1.$
$A$ is a column matrix.
