What is the expansion of $1/(15+5z)$ valid for $|z|>3$?

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Ok, I know this question is cheese! But I am stuck at this for the past two hours. Getting different answers after the expansion. Here's what I know: $1/(1-z) = -1/z -1/z^2 - \cdots$ valid for $|z|>1$. This series will be used.

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Write $$\frac{1}{15+5z} = \frac{1}{15} \frac{1}{1+\frac{z}{3}} = \frac{1}{15} \frac{1}{1-\frac{-z}{3}}$$