The domain of a function is the set of all values for which the function is defined. Sometimes it is easier to find the set of values for which the function is undefined and then say the domain is everything else. Polynomials are defined for all real numbers, so the only thing that would make this rational expression undefined would be a zero denominator. Set the denominator equal to zero and then solve the resulting quadratic equation. The two roots of the quadratic are the values to exclude. The domain is then the set of all real numbers except those two values.
