Answer:
f(0) = 0
f(n) = 2n-1 for n = 1, 2, 3,....
f(n) = -2n for n = -1, -2, -3,...
Step-by-step explanation:
Since integers and natural numbers are both infinite numerable, they can be arranged in sequences
0, 1, -1, 2, -2, 3, -3, 4, -4,...
0, 1, 2, 3, 4, 5, 6, 7, 8,...
So the map that assigns to each integer the natural below it in the arrange showed above, is clearly a one-to-one map.
This map could be described as
f(0) = 0
f(n) = 2n-1 for n = 1, 2, 3,....
f(n) = -2n for n = -1, -2, -3,...
