## Elementary Algebra

$3x(x+1)(x-1)$
Since $3x$ is common to all the terms in the expression, we obtain: $3x^{3}-3x$ =$3x(x^{2}-1)$ Now, we use the relation $a^{2}-b^{2}=(a+b)(a-b)$ to simplify: $3x(x^{2}-1)$ =$3x(x^{2}-1^{2})$ =$3x(x+1)(x-1)$