Here is a fairly clear and quick explanation of simplifying rational expressions as well as a discussion about domain.
An example problem that involves the factoring of a polynomial. And a different explanation of some rules for simplifying.
Source: jcmaslan
A slightly more challenging example of rational expressions with two quadratics. More importantly, there's a great discussion of how to factor quadratics by grouping.
Source: Khan Academy
A discussion on finding least common multiples with several examples.
Several examples (from easy to slightly more complex) of solving rational equations.
Source: Khan Academy
This a great reference sheet for this unit as well as many others.
