## anonymous one year ago Find the sum of the infinite geometric series 8 + 4 + 2 + 1 +...

1. jim_thompson5910

|dw:1433381103015:dw|

2. jim_thompson5910

|dw:1433381109007:dw|

3. jim_thompson5910

|dw:1433381124919:dw|

4. jim_thompson5910

Rule $\Large \sum_{k=1}^{\infty}a*r^{k-1} = \frac{a}{1-r}$ if and only if |r| < 1. Since r = 0.5, that makes |r| < 1 true, which allows us to use the formula

5. anonymous

I'm confused, do I used that equation to find the sum? If so what is a?

6. jim_thompson5910

I posted what 'a' was in my second post above

7. jim_thompson5910

a = first term

8. jim_thompson5910

a = 8 is the first term r = 0.5 is the common ratio you use $\Large S = \frac{a}{1-r}$

9. anonymous

So the sum is 16?

10. geerky42

Yes.

11. jim_thompson5910

yep S = 16