You can use the convert program (included with imagemagick) to convert a LaTeX file to an image:

$ convert -density 144 -geometry 100% source.dvi dest.jpeg

This is the format for a basic LaTeX document:

documentclass{article}
\begin{document}
...
end{document}

You can turn off paragraph indentation (which is on by default) and increase the space between paragraphs to indicate where they begin and end:

\setlength{\parindent}{0.0in}
\setlength{\parskip}{0.1in}

Use the eqnarray environment to typeset a list of equations:

\begin{eqnarray}
... \
... \
...
end{eqnarray}

(No $$ or $ is required to typeset the equations.)

Inline:

$x^2 = y$

Block-level:

$$sum_{i=1}^{n} {i}$$