A power series from $\frac{x}{9+x^2}$ I need to make power series from $\frac{x}{9+x^2}$, and I don't have any idea how.
The only thing I know is how to make power series from $\frac{1}{1-q}$.
Thank you!

$$\frac{x}{9+x^2}=\frac{x}{x^2(1+\frac{9}{x^2})}=\frac{1}{x}\frac{1}{1+(\frac{3}{x})^2}=\frac{1}{x}\sum_{j=0}^\infty\left(-\left(\frac{3}{x}\right)^2\right)^j$$
