Answer
$\color{blue}{(x^2+4)(x+2)(x-2)}$
Work Step by Step
Note that $x^4=(x^2)^2$ and $16=4^2$.
Thus, the given binomial is equivalent to:
$=(x^2)^2-4^2$
Factor using the formula $a^2-b^2=(a+b)(a-b)$ where $a=x^2$ and $b=4$ to obtain:
$=(x^2+4)(x^2-4)
\\=(x^2+4)(x^2-2^2)$
Factor the second binomial factor using the same formula above with $a=x$ and $b=2$ to obtain:
$=\color{blue}{(x^2+4)(x+2)(x-2)}$
