Chapter 8

Rational Functions

A rational function is special in that the function rule involves a fraction with a polynomial in both the numerator and the denominator. Rational functions have restrictions in their domain; any value creating a 0 in the denominator has to be excluded. Many of these exclusions are identified as vertical asymptotes. The x-intercepts of rational functions can be solved for by setting the numerator equal to 0; this is done after you’ve determined that there are no common factors in the numerator and denominator. A rational function can have a horizontal asymptote — as long as the highest power in the numerator is not greater than that in the denominator.

The Problems You’ll Work On

In this chapter, you’ll work with rational functions in the following ways:

Determining the domain and range of the function

Removing discontinuities, when possible

Finding limits at infinity and infinite limits

Writing equations of vertical, horizontal, and slant asymptotes