- #1

zeion

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## Homework Statement

Find the positive numbers r for which [tex]\sum \frac{r^k}{k^r}[/tex] converges.

## Homework Equations

## The Attempt at a Solution

What method do I use for this?

[tex]\frac {a_{k+1}}{a_k} = \frac {r^{k+1}}{(k+1)^r} \cdot \frac{k^r}{r^k}

= r \cdot (\frac{1}{k})^{\frac{r}{k}} [/tex]