Sum of infinite geometric series with two terms in summation

Question

I have an infinite geometric series:
$$\sum_{i=1}^{\infty} \frac{r^i}{(1+d)^i},$$
where $d$ is a constant. I would like to use the sum of infinite geometric series formula, but I cannot see how to use it because of the $(1+d)^i$ term. How could I calculate this sum?

Thanks.

Answer 1

Express it as $$ \sum_{i=1}^\infty \left( \frac{r}{1+d}\right)^i $$ which is geometric, albeit with a different common ratio.