A= 3+32+33+...+32016
3A=32+33+34+....+32017
3A-A=(32+33+34+...+32017)-(3+32+33+...+32016)
2A=32017-3
A=\(\frac{3^{2017}-3}{2}\)
Ta có:
A = 3 + 32 + 33 + .......+ 32016
=> 3A = 32 + 33 + 34 + .....+ 32017
Do đó 3A - A = 32017 - 3
2A = 32017 - 3
A = \(\frac{3^{2017}-3}{2}\)