Concretely for f(x) =, this function takes only TWO values: if x > 0, then |x| = x, and therefore f(x) = = 1. if x = 0, then the function f(x) is NOT DEFINED. if x < 0, then |x| = -x, hence f(x) = = -1. So, the range of this function is the set of the two values {-1,1}, while its domain is the set of all real numbers except of {0}.