Let: $f(x)=\lim\_\limits{n\to \infty}\frac{x^n}{x^n+3}.$

I need to calculate:

* $\lim\_{x \rightarrow 1^{+}} f(x)$
* $\lim\_{x \rightarrow 1^{-}} f(x)$
* $\lim\_{x \rightarrow (-1)^{+}} f(x)$
* $\lim\_{x \rightarrow (-1)^{-}} f(x)$

I have no idea how to deal with this kind of questions. I'd like to some directing or hints.