How do you determine the range of the following relations given the domain?

Question

a) x------- x+3, x = 0, 1, 2, 3
b) x------- 1/2 x x= -2,-1,0,1,2
c) x------- 2x, x= -2,-1,0,1,2

Answer 1

Use the rule indicated (such as f(x) = x + 3), to calculate the f(x)) value for each x.

It appears that they are assuming a limited set of discrete numbers for both domain and range. I find this kind of math teaching a rather confusing waste of time.