\documentclass[leqno,a4paper]{article}
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\usepackage{amsmath}
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\usepackage{titlesec}
\usepackage{graphicx}
%\usepackage{auto-pst-pdf}
\usepackage{makeidx}
\usepackage{boxedminipage}

\graphicspath{
  {.}
  {figuras/}
  {figuras/texfiles/}
  {figuras/epsfiles/}
}
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\numberwithin{equation}{section}
\date{}
\begin{document}
\section{Introducción}
\end{document}