the machine in this question is the machine which takes a number, multiplies it by 2, then adds 3 to the resul

Question

for which possible choices of the sets XandY is this machine a function from X to Y
A) x= set of positive integers, y = set of positive real numbers
B) x=set of integers, y=set of real numbers
C) x=set of positive integers y=set of positive real numbers
D) x=set of positive integers y= set of positive integers

Answer 1

None of the above. X does not have to be an integer and can be any real number. For that matter, I suppose it could be an imaginary number, too.

Answer 2

I am sure the 2 previous answers make you very happy! First I didn't get the difference between A and C. Apart from that in all your examples, if you take t in x, then 3t+2 is in y, which is all you want. So the answer is indeed all of the above.

Answer 3

All of these.

You only need one example of each type to show it so.