Answer
$28$
Work Step by Step
RECALL:
(1) $(a-b)(a+b) = a^2-b^2$
(2) $i^2=-1$
Use rule (1) above with $a=5$ and $b=i\sqrt{3}$ to obtain:
$=5^2 - (i\sqrt{3})^2
\\=25 - i^2(3)$
Use rule (2) above to obtain:
$=25 - (-1)(3)
\\=25-(-3)
\\=25+3
\\=28$
