## Precalculus (6th Edition)

$\color{blue}{(x^2+4)(x+2)(x-2)}$
With $16=4^2$ and $x^4=(x^2)^2$, the given expression is equivalent to: $=(x^2)^2-4^2$ RECALL: $a^2-b^2=(a+b)(a-b)$ Factor the expressions using the formula above with $a=x^2$ and $b=4$ to obtain: $=(x^2+4)(x^2-4) \\=(x^2+4)(x^2-2^2)$ Factor the second binomial using the same formula to obtain: $=\color{blue}{(x^2+4)(x+2)(x-2)}$