\begin{figure}[t]
\centering
\begin{tikzpicture}[scale=2]


  \draw[->] (-0.2,0) -- (4,0) node[right] {$x$};
  \draw[->] (0,-0.2) -- (0,4) node[above] {$f(x)$};



  \draw (.2,4) parabola bend   (.8,.5) (4,.2)  node[below right] {$$};
\end{tikzpicture}

\label{fig:parabola}
\end{figure