\documentclass[12pt,a4paper]{article}
% Additional class options can be given in brackets. Here we set the
% main font size, and the page size.
% This time we include some title information.
\title{A \LaTeX{} example}
\author{\'Eamonn Murray}
\date{\today}
\begin{document}
% The maketitle command will generate a title from the information defined
% in the header above.
\maketitle
% We can use the section command to divide the document into sections.
% subsection, and subsubsection can also be used to further subdivide
% sections.
\section{Introduction}
Equation \ref{geometric_sum} below shows another way to include mathematical
expressions. It is given a label so it can be referred to in this paragraph.
\begin{equation}\label{geometric_sum}
\sum_{i=0}^{\infty} z^k = \frac{1 - z^{n+1}}{1 - z}
\end{equation}
\section{Conclusion}
Conclusions go here.
\end{document}