Exercise 3 Page 331

Let's consider the following pair of rational functions. The domain of $f(x)$ is all real numbers such that $q(x)\ne 0,$ and the domain of $g(x)$ is all real number such that $s(x)\ne 0.$ Next, let's find the sum and difference of the two functions above. Since we got a rational function, we have to exclude the values that make the denominator zero. We see above that the domain of the sum or difference of two rational functions is all the real numbers such that $q(x)\ne 0$ and $s(x)\ne 0.$

The domain of the sum or difference of two rational functions is the intersection of the domains of both functions.