Domain and Range of Rational Functions
It is now time to use the skills you acquired in the warm-up for this section to help find the domain and range of rational functions. Remember that domain is all the possible values of x while range is all the possible values of y. Looking back at the warm-up and the equation 
, we found that x = -3 and y = 1 do not work in the equation. They are the asymptotes. This means that the domain is All Real Numbers except x = -3 and the range is All Real Numbers except y = 1.
Remember, you can’t have zero in the denominator, therefore x + 3 ≠ 0. This can only happen when x = -3, therefore, x = -3 is an excluded value.
Also, the graph moves up 1 unit. This means that the horizontal asymptote is at y = 1. This also becomes an excluded value.