#### Answer

prime; the sum of the two squares does not factor.

#### Work Step by Step

Kaitlin tried to apply the formula $a^2-b^2=(a+b)(a-b)$, but she used $a^2+b^2$ instead. Here, the sum of the two squares does not factor. Therefore, the binomial is prime.
$16a^2+81$
prime; the sum of the two squares does not factor.