Question

Which function forms an arithmetic sequence when x = 1, 2, 3, ...?

Answer 1

The first one is arithmetic sequence  as each term decreases by same amount 
(1/3)  as x = 1,2,3,4...

Answer 2

Which Function Forms an Arithmetic Sequence When x = 1, 2, 3, ...?
f(x)=-x/3+5