The domain of a function is the set of numbers for which the function is defined. For a rational function, the domain is the set of all real numbers except any number(s) that would make a denominator equal zero.
You can put this solution on YOUR website! When you answer a domain question you must think what numbers can I put in for x in the function or what numbers can't I put in for x in the function. In this case you could use any real number except for 1 because 1 would make the denominator zero and division by zero is undefined. Therefore the domain is all the reals except 1.