Answer:
-i
Explanation:
The imaginary unit i is defined by the property that
. With that in mind, we can list the first few powers of i:

Notice how
is the same as
? The powers of i are cyclic: they repeat every 4 powers. In general, for any power of i
:
if
has remainder 0
if
has remainder 1
if
has remainder 2
if
has remainder 3
, so
