Bias-variance

\documentclass[12pt,border=5pt]{standalone}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}
\usetikzlibrary{calc,angles,quotes,positioning,decorations.markings,arrows.meta,patterns,intersections,shapes,trees}
\usepackage{amsmath,amssymb}
\begin{document}
\begin{tikzpicture}
    \begin{axis}[
        legend pos=north east,
        axis x line=middle,
        axis y line=middle,
        width=8cm,
        height=8cm,
        %grid style={dashed, gray!30},
        xmin= 0,     % start the diagram at this x-coordinate
        xmax= 2,    % end   the diagram at this x-coordinate
        ymin= 0,     % start the diagram at this y-coordinate
        ymax= 2,   % end   the diagram at this y-coordinate
        xlabel=error,
        ylabel=model comlexity,
        ticks=none,
        xticklabels={,,},
        yticklabels={,,},
        x label style={at={(axis description cs:0.5,-0.05)},
                       anchor=north},
        y label style={at={(axis description cs:-0.05,0.5)},
                       anchor=south,
                       rotate=90},]
      % plot it
      \addplot[domain=-0.29:2,samples=500,very thick] {1/(x+0.3)-0.2};
      \addplot[domain=0:2, red, very thick,samples=500] {3*(x-2)*x+3.8};
      \addlegendentry{training error}
      \addlegendentry{validation}
    \end{axis}
\end{tikzpicture}
\end{document}