# Homework Help: Radius of Convergence

1. Sep 29, 2010

### jegues

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

See figure attached for problem statement as well as my attempt.

2. Relevant equations

3. The attempt at a solution

See 2nd figure attached.

I don't know how to rid myself of that last n! I've got kicking around in the numerator.

Any ideas?

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2. Sep 29, 2010

### jav

Check your an+1 term. The [(n+1)!] should be squared.

3. Sep 29, 2010

### jegues

Doh!

Thank you!

4. Sep 29, 2010

### jegues

Just to make sure I finished the question off right, we should find that R = -1, correct?

Then the open interval of convergence is,

$$|x-7| < -1$$

or $$1 < x-7 < -1$$ or $$8 < x < 6$$