The first term is given, so
1. The first term is 5.
          5 times the common ratio 2 is 10, so 
2. The second term is 10.
         10 times the common ratio 2 is 20, so 
3. The third term is 20.
         20 times the common ratio 2 is 40, so 
4. The fourth term is 40.
So the first four terms are 5, 10, 20, 40.
Edwin