Answer :
the domain of a(x) is I, positive integers (stated in the question)
the range of a(x) is all positive integers >2
the range of a(x) is all positive integers >2
so all positive integers is the domain (the number you can use)
and the range (the numbers you get when you put the numbers in the domain in) is all positive integers more than 2
and the range (the numbers you get when you put the numbers in the domain in) is all positive integers more than 2