LaTeX Forum

\documentclass[parskip=half]{scrartcl}
\usepackage[T1]{fontenc}

\PassOptionsToPackage{svgnames}{xcolor}
\usepackage{tikz}
\usepackage{bm}

\usepackage{lmodern}
\usepackage{microtype}

\begin{document}
  \begin{tikzpicture}[domain=0:4]
    \draw [->] (0,0) -- (4,0) node[right] {$\textcolor{brown}{\bm{x_1}}$};
    \draw [->] (0,0) -- (0,4) node[above] {$\textcolor{magenta}{\bm{x_2}}$};
    \draw[orange] plot (\x,{-\x+3.5});
  \end{tikzpicture}
\end{document}

\documentclass[tikz]{standalone}
\newcommand{\pmb}{}% unbekannter Befehl

\begin{document}
\begin{tikzpicture}
\draw [->] (0,0) -- (4,0) node[right, text=brown] {$\pmb{x_1}$};
\draw [->] (0,0) -- (0,4) node[above, text=magenta] {$\pmb{x_2}$};% Der mathematische Modus endet bei Dir an der falschen Stelle.

\draw[orange, domain=0:4]  plot (\x, {-\x+3.5});% Beim zweiten x fehlt der Backslash.
\draw [orange, very thick] (0,3.5) -- (3.5,0);
\end{tikzpicture}
\end{document}

\begin{tikzpicture} 
\hspace*{1cm}
\draw [->] (0,0) -- (4,0) node[right] {$\textcolor{brown}{\pmb{x_1}}$};
\draw [->] (0,0) -- (0,4) node[above] {$\textcolor{magenta}{\pmb{x_2}}$;

%\draw[orange, domain=0:4]  plot (\x, {-x+3.5});
\draw [orange, very thick] (0,3.5) -- (3.5,0);

\end{tikzpicture}

\documentclass{standalone}
\usepackage{tikz}
\usepackage{mathtools}
\begin{document}
\begin{tikzpicture}[scale=3]
    % axis
    \draw[thin,-latex] (0,0)  -- (1.5,0) node(xline)[below] {$x_1$};
    \draw[thin,-latex] (0,0) -- (0,1.5) node(yline)[left] {$x_2$};
    % Lines
    \draw[] (0,1) node[left] {$\dfrac{y}{p_2}$} -- (1,0) node[below] {$\dfrac{y}{p_1}$};
    \draw[dashed] (0,.5) node[left] {$x_2^*$} -| (.5,0) node[below] {$x_1^*$};
    \draw[fill] (.5,.5) circle (.5pt) node[xshift=.75cm] {$-\dfrac{p_1}{p_2}$};
    \draw (0.5,0.5) arc(45:90:-1);
    \draw (0.5,0.5) arc(45:0:-1);
\end{tikzpicture}
\end{document}

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{arrows}
\begin{document}
\begin{tikzpicture}[
    scale=5,
    axis/.style={very thick, ->, >=stealth'},
    important line/.style={thick},
    dashed line/.style={dashed, thin},
    pile/.style={thick, ->, >=stealth', shorten <=2pt, shorten
    >=2pt},
    every node/.style={color=black}
    ]
    % axis
    \draw[axis] (-0.1,0)  -- (1.1,0) node(xline)[right]
        {$x_2$};
    \draw[axis] (0,-0.1) -- (0,1.1) node(yline)[above] {$x_1$};
    % Lines
    \draw[important line] (.15,.15) coordinate (A) -- (.85,.85)
        coordinate (B) node[right, text width=5em] {$Y^O$};
    \draw[important line] (.0,.85) coordinate (C) -- (.85,.15)
        coordinate (D) node[right, text width=7em] {$\mathit{NX}=x$};
    % Intersection of lines
    \fill[red] (intersection cs:
       first line={(A) -- (B)},
       second line={(C) -- (D)}) coordinate (E) circle (.4pt)
       node[above,] {$A$};
    % The E point is placed more or less randomly
    \fill[red]  (E) +(-.075cm,-.2cm) coordinate (out) circle (.4pt)
        node[below left] {$B$};
    % Line connecting out and ext balances
    \draw [pile] (out) -- (intersection of A--B and out--[shift={(0:1pt)}]out)
        coordinate (extbal);
    \fill[red] (extbal) circle (.4pt) node[above] {$C$};
    % line connecting  out and int balances
    \draw [pile] (out) -- (intersection of C--D and out--[shift={(0:1pt)}]out)
        coordinate (intbal);
    \fill[red] (intbal) circle (.4pt) node[above] {$D$};
    % line between out og all balanced out :)
    \draw[pile] (out) -- (E);
\end{tikzpicture}
\end{document}