Question 81
Find all functions $f: \mathbb{R} \to \mathbb{R}$ which satisfy the conditions:
$$
f(x+y) \lt f(x) + f(y),
$$
$$
f(f(x)) = [x] + 2.
$$
$$
f(x+y) \lt f(x) + f(y),
$$
$$
f(f(x)) = [x] + 2.
$$
MathNet 2012 Question 81
Math Olympiad Vault · MathNet 2012