Answer
$30$
Work Step by Step
Using $(a+b)(a-b)=a^2-b^2$ or the product of the sum and difference of like terms, the expression $
(\sqrt{14}-4i)(\sqrt{14}+4i)
$ simplifies to
\begin{array}{l}
(\sqrt{14})^2-(4i)^2
\\=
14-16i^2
\\=
14-16(-1)
\\=
30
.\end{array}