You can put this solution on YOUR website! The domain of x would be whatever x is that won't make the denominator zero. So let's start like this: . Now since the domain of x is whatever x is that won't make the denominator zero, let's focus just on the denominator. First factor it. It is the difference between two perfect squares, so it is . Now take each expression separately as and . Set them both equal to zero. and . Solve both of them and get 3 and -3. These values for x are what x is to make the denominator zero. Therefore, these values are what x cannot be in this function. So the domain of x would be any value for x except those two. Domain: all x except 3 and -3.