Question 7
Determine the continuous functions $f : \mathbb{R} \to \mathbb{R}$ having the property that
$$
f\left(x + \frac{1}{n}\right) \le f(x) + \frac{1}{n}, \text{ for all } x \in \mathbb{R} \text{ and } n \in \mathbb{Z}^*.
$$
$$
f\left(x + \frac{1}{n}\right) \le f(x) + \frac{1}{n}, \text{ for all } x \in \mathbb{R} \text{ and } n \in \mathbb{Z}^*.
$$