If one part of the formula is undefined at X=2 then it is likely that the function is undefined there. You should however be careful to check whether the formula can be simplified. For example, (X^2-4)/(X-2) is undefined at 2, but you can extract a factor of X-2 from numerator and denominator to get X+2, which is defined at X=2. This is a very simple example of a removable singularity.