Hi guys,

I am a little stuck on where to begin here and any help would be great.

This is the question I am faced with:

Now, the formula I have been using recently for working out the sum of a geometric series to n places is:Quote:

The sum of the first three terms of a geometric series is http://mathbin.net/equations/31707_1.png. The sum of the first six terms is http://mathbin.net/equations/31707_2.png. Find the first term and common ratio.

$\displaystyle S_{n} = \frac{a(1-r^n)}{1-r}$

But I am unsure how to use it in this context.

Thanks for any help!