Answer
$3(x+5)(x-5)$
Work Step by Step
Factoring the $GCF=3,$ the given expression, $
3x^2-75
,$ is equivalent to
\begin{align*}\require{cancel}
&
3(x^2-25)
.\end{align*}
Using the factoring of the difference of $2$ squares which is given by $a^2-b^2=(a+b)(a-b),$ the expression above is equivalent to
\begin{align*}
&
3[(x)^2-(5)^2]
\\&=
3[(x+5)(x-5)]
\\&=
3(x+5)(x-5)
.\end{align*}
The factored form of the given expression is $
3(x+5)(x-5)
.$
