Question

i^84

Answer 1

84 can be divided by 4, and you get a whole number.

Answer 2

You know the rule that for any positive integer n,

\(\large\color{midnightblue}{ \rm i^{4n}=1 }\)

Answer 3

In your case, \(\large\color{midnightblue}{ \rm i^{4(21)}=1 }\) (21 instead of n )