Limitations on the domain of a function take the form of zeros in the denominator, negative numbers under a square root sign, and the like. Here we have a fraction so we want to look at where the denominator goes to zero.

So the denominator is zero at x = 2 and x = 4. Thus these values for x cannot be in the domain. This is our only restriction, so the domain will be:

or, more simply, "all real x except 2 and 4."

-Dan