Answer
$89+0i$
Work Step by Step
First of all, recall that $i=\sqrt{-1}$, so $i^{2}=-1$
Also, since $(a+b)(a-b)=a^{2}-b^{2}$, we obtain:
$(-5-8i)(-5+8i)$
=$(-5)^{2}-(8i)^{2}$
=$25-64i^{2}$
=$25-64(-1)$
=$25+64$
=$89$
Since we have to write the answer in the form $(a+bi)$, we write:
$89=89+0i$
