## College Algebra (6th Edition)

$2(x^{2}+9)(x^{2}-9)$
We are given the expression $2x^{4}-162$. First, we can use the distributive property to factor out 2, the greatest common factor of both terms. $2x^{4}-162=2(x^{4}-81)$ If $a$ and $b$ are real numbers, we know that $a^{2}-b^{2}=(a+b)(a-b)$ Therefore, $2(x^{4}-81)=2(x^{2}+9)(x^{2}-9)$. In this case, $a=x^{2}$ and $b=9$.