Question 85
Find all continuous functions $f : \mathbb{R} \to \mathbb{R}$ that satisfy conditions:
$f(0) = 0$ and $\forall x \in \mathbb{R}: f(2x) \geq x + f(x)$, $f(3x) \leq 2x + f(x)$.
$f(0) = 0$ and $\forall x \in \mathbb{R}: f(2x) \geq x + f(x)$, $f(3x) \leq 2x + f(x)$.