I try to solve a geometric sum, but I'm stuck. The original terms are:
$$s = 9 - \frac{9}{2} + \frac{9}{4} - \frac{9}{8} + \cdots - \frac{9}{128}$$
After some work I found that the sum would be:
$$\sum_{k=1}^8 \frac{-18}{(-2)^k}$$
My next step towards finding the sum of all terms is to use the general formula. However, this includes getting the quotient, and I don't understand how to do so in this type of scenario.