Answer
$3(t+1)(t-1)$
Work Step by Step
Factoring the $GCF=
3
$, the given expression, $
3t^2-3
,$ is equivalent to
\begin{array}{l}
3(t^2-1)
\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, $
3(t^2-1)
,$ is
\begin{array}{l}
3(t+1)(t-1)
\end{array}