Give an example of a function whose domain is{3,4,7,9} and?

Question

whose range is {-1,0,3}
plese give me the trick of finding such functions
Is this answer coreect
the function must only consist of individual points:
{(3, -1), (4, 0), (7, 3), (9, 0)}
is an example.

Answer 1

no telling how the numbers are paired up. The points you give would fit the requirements, though.