Answer
$6(a+2)(a-2)$
Work Step by Step
Factoring the $GCF=
6
$, the given expression, $
6a^2-24
,$ is equivalent to
\begin{array}{l}
6(a^2-4)
\end{array}
Using $x^2-y^2=(x+y)(x-y)$ or the factoring of the difference of 2 squares, then the factored form of the expression, $
6(a^2-4)
,$ is
\begin{array}{l}
6(a+2)(a-2)
\end{array}