\documentclass{standalone}
\pagestyle{empty}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}[scale=2]

\draw[thick]  (-2,0)--(2,0);

\draw[red] (-1,0)--(0,1)--(0,2);
\draw[red] (1,0)--(0,1);



\node at (-1.5,.5) {$u=2$};
\node at (1.5,.5) {$u=-2$};
\node at (0,.5) {$u=0$};


\clip (-2,-.05) rectangle (2,2);
\foreach \j in {-1.5,-2, ...,-4} \draw[very thin, cyan] (\j,0)--(0,-\j)--(-\j,0);


\clip (-1,0)--(0,1)--(1,0);
\foreach \j in {-.5,0,.5} \draw[very thin, cyan] (\j,0)--(\j,1);




\end{tikzpicture}
\end{document}

