Answer
$58+0i$
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:
$(7-3i)(7+3i)$
=$(7)^{2}-(3i)^{2}$
=$49-9i^{2}$
=$49-9(-1)$
=$49+9$
=$58$
Since we have to write the answer in the form $(a+bi)$, we write:
$58=58+0i$
