Answer
$3x(x+2)(x-2)$.
Work Step by Step
The given polynomial is
$= 3x^3-12x$
Factor out $3x$.
$= 3x(x^2-4)$
Write the the polynomial as $a^2-b^2$.
$= 3x(x^2-2^2)$
Use difference of two square pattern
$a^2-b^2=(a+b)(a-b)$.
We have $a=x$ and $b=2$.
$= 3x(x+2)(x-2)$
Hence, the complete factor of the polynomial is $3x(x+2)(x-2)$.
