## anonymous one year ago Find the sum of a finite geometric sequence from n = 1 to n = 6, using the expression −2(5)n − 1

1. anonymous

@hwyl can you help?

2. anonymous

$\sum_{n=1}^6-2(5)^{n-1}$?

3. anonymous

i mean is that the question?

4. anonymous

i think so.. i don't remember how to do this

5. anonymous

pull the minus two out first, deal with it at the end

6. anonymous

$\sum_{n=1}^6-2(5)^{n-1}=-2\sum_{n=1}^6(5)^{n-1}$

7. anonymous

then $\sum_{n=1}^6(5)^{n-1}=\frac{5^6-1}{5-1}$ compute that, multiply the restult by $$-2$$