Let's analyze the provided graph and solve the corresponding questions:

Part a) Calculer les limites à gauche et à droite de cette fonction aux points spécifiés.

We need to compute the limits of $f(x)$ at $x = 0$, $x = 18$, and their respective one-sided limits.

1. $\lim\limits_{x \to 0} f(x)$: From the graph, as $x \to 0$ from both sides, the function approaches $-2$. $\lim_{x \to 0} f(x) = -2$

2. **(\lim\limits_{x \to 0^-} f(x