mrv4.tex

\documentclass{article}
\usepackage{pgfplots}
\usepackage{tikz}

\pgfplotsset{compat=1.5.1}

\begin{document}
\begin{figure}
\begin{tikzpicture}
\begin{axis}[ 
    ticks=none,
    axis lines = middle,
    axis line style={->},
    ymin=-1.3, ymax = 1.3,
    xmin=-1.3, xmax=1.3,
    xlabel={$x$},
    ylabel={$y$},
    axis equal image,
    samples = 500
]
\addplot[black, 
         fill = blue, 
         fill opacity = 0.5, 
         domain = -1.3:1.3] {1 - x};
\addplot[black, 
         fill = blue, 
         fill opacity = 0.5, 
         domain = -1.3:1.3] {-1 - x};
\node [rotate = -45] at (axis cs:0.6,0.6) {$y=1-x$};
\node [rotate = -45] at (axis cs:-0.4,-0.4) {$y=-1-x$};
\draw[dashed,
      fill = blue,
      fill opacity = 0.5] (axis cs:0,1) -- (axis cs:-1,1) -- (axis cs:-1,0) -- (axis cs:0,-1) -- (axis cs:1,-1) -- (axis cs:1,0) -- (axis cs:0,1);
\addplot[red, 
         mark = *, 
         only marks] coordinates {(-1,1) (1,1) (1,-1) (-1,-1)};
\addplot[mark = ""] coordinates {(-1, 1)} node[above] {(-1,1)};
\addplot[mark = ""] coordinates {(1, 1)} node[above] {(1,1)};
\addplot[mark = ""] coordinates {(-1, -1)} node[below] {(-1,-1)};
\addplot[mark = ""] coordinates {(1, -1)} node[below] {(1,-1)};
\draw[dashed] (axis cs:-1,-1) -- (axis cs:0,-1) -- (axis cs:-1,0) -- (axis cs:-1,-1);
\draw[dashed] (axis cs:1,1) -- (axis cs:1,0) -- (axis cs:0,1) -- (axis cs:1,1);
\end{axis}
\end{tikzpicture}
\end{figure}
\end{document}