Question 7564
Definition of domain : Set all values of 'x' for  which f(x) is defined 
 f(x) is defined at x= a means f(a) may be positive or negative or zero.
 Example f(x) = 1/x  f(2) = 1/2 = 0.5 implies f(x) is defined at x = 2
         f(0) = 1/0 = no value implies f(x) is not defined at x = 0.