## anonymous one year ago Find the sum of a 9-term geometric sequence when the first term is 4 and the last term is 1,024.

1. anonymous

@mathmate

2. anonymous

@Preetha

3. mathmate

Here's an article to familiarize yourself with geometric sequences and sums. If you encounter problems while solving, please post again. Hint: in a geometric sequence, $$ar^0=a$$ is the first term, r is the common ratio, and $$ar^{n-1}$$ is the nth term. So the nineth term divided by the first term equals $$\Large \frac{ar^{9-1}}{ar^{0}}=r^8$$ This will allow you to solve for r.

4. anonymous

why thank you, let me try it out and I'll ask you for help if needed c:

5. mathmate

Here's the link that I forgot to post: http://www.mathsisfun.com/algebra/sequences-sums-geometric.html

6. anonymous

alright so I have a 113.77778 added to the last term but it comes out to 1027 in the ninth term. Could I get some guidance here?

7. mathmate

If you solve r^8=1024/4, you should find an integer value for r (whole number). The rest will work well from there.

8. anonymous

that means r = 2, but that makes the 8th term 1,024

9. anonymous

things got all out of wack, sorry, I should have tried counting better, it was r = 2 the whole time. Thank you for your time.