# Excluded Values and Domain of Rational Functions

### By: Ashley Cooper, Jentel Strand, Antia Dickens

When finding the excluded values of a function you are looking for the numbers that make the denomenator equal zero. Because of this, you first have to set the denomenator equal to zero. After this, you have to factor the equation. Then the factors to equal to zero and solve. These answers are the excluded values. The domain will be the numbers the can't make the denomenator equal zero (excluded values). To write the domain you will write x≠the excluded values.

Example 1) Find the excluded values and the domain of

The domain of the function is all real numbers except 1 and 3. This can be written in interval notation as (−∞,1)U(1,3)U(3,∞).

Example 2) Find the excluded values and the domain of

The domain of the function is all real number except 1 and 5. This can be written in interval notation as (−∞,1)U(1,5)U(5,∞).

Example 3) Find the excluded values and the domain of

The domain of the function is all real numbers except 1. This can be written in interval notation as (−∞,1)U(1,∞).