Given a function of the form
$$f(x)= \frac{c_1}{x} + \frac{c_2}{x^2} \,+ \,...+\, \frac{c_n}{x^n}$$
where $c_1,c_2,...,c_n \epsilon \mathbb{R}$ are constants, as $x$ approaches $0$ it is clear that $\frac{c_n}{x^n}$ dominates.
So could I say that as $x$ approaches $0,\,f(x)=\mathcal{O}\, (\frac{1}{x^n})$?