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

\begin{document}

\begin{tikzpicture}[scale=2]

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

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

\node at (-1.5,.5) {$u=1$};
\node at (1.5,.5) {$u=1$};
\node at (0,.5) {$u=\frac{x}{t}$};



\node at (-.65,.25) {$u=-1$};
\end{tikzpicture}
\end{document}
