Help needed with the ratio test

1. Dec 1, 2009

thomas12323

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

The problem is looking for the radius of convergence
sum(5^n)((x-3)^n)/n
n=1
2. Relevant equations

3. The attempt at a solution

2. Dec 1, 2009

Staff: Mentor

What work have you done in using the ratio test?

3. Dec 1, 2009

thomas12323

I broke it down to (x-3)n/(n+1)

4. Dec 1, 2009

Staff: Mentor

That's not right. What happened to the 5^n factor?
You should have this as part of your work.
$$\lim_{n \to \infty} \left(\frac{5^{n + 1}(x - 3)^{n + 1}}{n + 1}~\frac{n + 1}{5^n (x - 3)^n}\right )$$