\begin{definition}[Definition:Partial Fractions Expansion]
Let $\map R x = \dfrac {\map P x} {\map Q x}$ be a rational function, where $\map P x$ and $\map Q x$ are expressible as polynomial functions.
Let $\map Q x$ be expressible as:
:$\map Q x = \ds \prod_{k \mathop = 1}^n \map {q_k} x$
where the $\map {q_k} x$ are themselves polynomial functions of degree at least $1$.
Let $\map R x$ be expressible as:
:$\map R x = \map r x \ds \sum_{k \mathop = 0}^n \dfrac {\map {p_k} x} {\map {q_k} x}$
where:
:$\map r x$ is a polynomial function which may or may not be the null polynomial, or be of degree $0$ (that is, a constant)
:each of the $\map {p_k} x$ are polynomial functions
:the degree of $\map {p_k} x$ is strictly less than the degree of $\map {q_k} x$ for all $k$.
Then $\map r x \ds \sum_{k \mathop = 0}^n \dfrac {\map {p_k} x} {\map {q_k} x}$ is a '''partial fractions expansion''' of $\map R x$.
\end{definition}