Transition from the second step to the third step?

[bondking2]

Homework Statement

How do you change from the second step to the third step?

Homework Equations

http://i158.photobucket.com/albums/t103/nh4444/Capture_zpspyxdwdna.jpg

The Attempt at a Solution

My guess is that it has something to do with the geometric series. I am not sure how to proceed.

 

[BvU]

Hello, your majesty,

That is not a problem statement in your 1. !
Nor is 2. a relevant equation !
And 3 is a guess, not an attempt at solution.

What's this about ? Could you please read the guidelines ?