
\begin{exercice}\`A partir des représentations graphiques des trinômes $f$ et $g$ définis sur $\mathbb{R}$, dresser leurs tableaux de variations.  
  \begin{center}\begin{tikzpicture}[general, xscale=0.8, yscale=0.42]
   \draw[quadrillage, xstep=0.5] (-2,-4) grid (6,6);
   \axeX{-2}{6}{1,2, 4}
   \axeY{-4}{6}{-2,2, 4}
   \origine
   \draw[color=A1, smooth, samples=200, domain=-0.54:6, epais] plot (\x,-0.4*\x*\x+2.4*\x-2.6);
   \draw[color=C1, smooth, samples=200, domain=1.15:6, epais] plot (\x,0.5*\x*\x-4.0*\x+10);
   \draw[color=A1] (5.5,-3) node {{\boldmath ${\cal C}_f$}};
   \draw[color=C1] (5.5,4) node {{\boldmath ${\cal C}_g$}};
  \end{tikzpicture}
  \end{center}
\end{exercice}