Domain and Range of Rational Functions
Finding the Domains of Rational Functions
A vertical asymptote represents a value at which a rational function is undefined, so that value is not in the domain of the function. A reciprocal function cannot have values in its domain that cause the denominator to equal zero. In general, to find the domain of a rational function, we need to determine which inputs would cause division by zero.
DOMAIN OF A RATIONAL FUNCTION
The domain of a rational function includes all real numbers except those that cause the denominator to equal zero.
HOW TO
Given a rational function, find the domain.
1. Set the denominator equal to zero.
2. Solve to find the -values that cause the denominator to equal zero.
3. The domain is all real numbers except those found in Step 2.
EXAMPLE 4
Finding the Domain of a Rational Function
Solution
Begin by setting the denominator equal to zero and solving.
The denominator is equal to zero when . The domain of the function is all real numbers except .
Analysis
A graph of this function, as shown in Figure 8, confirms that the function is not defined when .
Figure 8
There is a vertical asymptote at and a hole in the graph at . We will discuss these types of holes in greater detail later in this section.
TRY IT #4
Source: Rice University, https://openstax.org/books/college-algebra/pages/5-6-rational-functions
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