# Homework Help: A difficult Series problem!

1. Apr 10, 2012

### gavin25

1. The problem statement, all variables and given/known data
Show that the series Ʃ 1 to ∞ ((-1)^n)*(n+1)/5^n converges using the alternating series test.

2. Relevant equations

3. The attempt at a solution
I don't know how to show the series is decreasing. I took the derivative of the function, but it got messy and I don't feel that was the correct way to go. Any help appreciated, thanks.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Apr 10, 2012

### LCKurtz

Have you played with the inequality you get when you write $a_{n+1}\le a_n$? Show us what you get...