3. We consider the function $f$ defined on $] 0 ; + \infty \left[ \right.$ whose representative curve $C _ { f }$ is given in an orthonormal coordinate system in the figure (Fig. 1) on page 5. We specify that:

\begin{itemize}
  \item $T$ is the tangent to $C _ { f }$ at point $A$ with abscissa 8;
  \item The $x$-axis is the horizontal tangent to $C _ { f }$ at the point with abscissa 1.
\end{itemize}

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{3ea119b1-a732-4e2a-a016-8c7712a58a8d-5_1020_1376_212_372}
\captionsetup{labelformat=empty}
\caption{Fig. 1}
\end{center}
\end{figure}

Statement 3: According to the graph, the function $f$ is convex on its domain of definition.\\