## anonymous one year ago Find S12 for the series 1 + 2 + 4 + 8 +.. i got 2048

1. anonymous

@Michele_Laino am i right

2. Michele_Laino

here we have a geometric series, whose first term is a1=1 and constant q= 2

3. anonymous

okay

4. Michele_Laino

so, we can apply this formula: $\Large {S_{12}} = {a_1}\frac{{1 - {q^{12}}}}{{1 - q}}$

5. anonymous

okay

6. Michele_Laino

after a substitution, i get this: $\Large {S_{12}} = {a_1}\frac{{1 - {q^{12}}}}{{1 - q}} = 1 \cdot \frac{{1 - {2^{12}}}}{{1 - 2}} = ...?$

7. anonymous

-4097

8. Michele_Laino

I got 4095

9. anonymous

nvm ur right, typo sorry lol

10. anonymous

so its 4095

11. Michele_Laino

yes!