TITLE: How is $-16/4i$ equal to $4i$?
QUESTION [6 upvotes]: I came across a problem: $-16/4i$. Every time I put it into a calculator, it comes out as $4i$, but when I try to solve it is $-4i$, because of the negative one in front of the $16$.

REPLY [2 votes]: Another way of doing it is:
$\frac{-16}{4i}$ Then reduce to get $\frac{-4}{i}$. We know that $i^2=-1$, there fore we can make it $\frac{4i^2}{i}$ and by reduceing again we get $4i$.