Notice that
so that for each power of 2, there is a pattern of period 4. This means that for integers
, each of 
, 
, 
, and 
have the same units digit.
We can write
, and since 
, it follows that 
and 
share the same units digits. So the units digit of 
is 8.
so that for each power of 2, there is a pattern of period 4. This means that for integers
We can write