When finding the domain of a function, remember it's all values for the variable where the function is defined.

For example, f(x) = 1/(x - 2), the domain is all real nubmers except for 2. A value of 2 for x makes the denominator 0 and the function undefined.

Be careful with some functions. Make sure everything is simplified before determining the domain. If

f(x) = (x^2 - 16)/(x - 4) it might be tempting to see the denominator and conclue the domain is all real numbers except for 4. But this is incorrect. 

If we factor the numerator, we get (x -4)(x + 4).  The (x - 4) in the numerator will cancel with the (x - 4) in the denominator.

Therefore f(x) = x + 4 and the domain is all real numbers.