# Homework Help: Find the interval of convergence for the given power series.

1. Apr 29, 2012

### MeMoses

1. The problem statement, all variables and given/known data

Find the interval of convergence for the given power series.
Sum from n=1 to infinty of (x-11)^n / (n(-9)^n)

2. Relevant equations

3. The attempt at a solution
I used the ratio test and I'm getting 2<x<20, but that doesn't seem to be right. I get abs(1/9*(x-11)) < 1, which simplifies into 2<x<20. I couldn't sworn I did this problem correctly, but I'm not getting the correct answer. Any help would be great.

2. Apr 29, 2012

### LCKurtz

That is the correct interval, but don't forget you have to check the two end points separately.

3. Apr 29, 2012

### MeMoses

Here the thing, I entered all possible compinations for the endpoints just to check my answer for the interval and they were all wrong. Just to double check it does not converge at 2 and does at 20, right?

4. Apr 29, 2012

### MeMoses

Ok it accepts my answer now. It was probably something on my end but thanks anyways.