In the denominator, you see .


In order for you will be able to take the square of a number, this number MUST be non-negative.


So, you first need to solve this inequality

     >= 0.


Factor left side

     >=0.


Either both factor should be negative, or both factors should be positive.


It gives you the solution set  x <= -2  or  x >= 1.


Also, x = -2 makes the denominator equal to zero, as well as the value x = 1.


Therefore, you must exclude them from the domain.


Finally, the domain is the union of two open intervals  (-oo,-2) U (1,oo).    ANSWER