\documentclass[12pt]{article}
% begin font setup
\usepackage[T1]{fontenc}
\usepackage{mathptmx}
\usepackage[scaled=.92]{helvet}
\usepackage{courier}
% end font setup
% begin other packages
\usepackage{textcomp}
\usepackage[intlimits]{amsmath}
% end other packages
\usepackage{color}
\setlength{\paperwidth}{20cm}
\setlength{\paperheight}{20cm}
\pagestyle{empty}
\setlength{\voffset}{-0.9in}
\setlength{\topmargin}{0bp}
\setlength{\headheight}{0bp}
\setlength{\headsep}{0bp}
\setlength{\topskip}{0bp}
\setlength{\hoffset}{-0.9in}
\setlength{\oddsidemargin}{0bp}
\setlength{\evensidemargin}{0bp}
\setlength{\marginparwidth}{0bp}
\setlength{\marginparsep}{0bp}
\setlength{\textwidth}{\paperwidth}
\setlength{\textheight}{\paperheight}
\setlength{\parskip}{0bp}
\setlength{\parindent}{0bp}
\setlength{\pdfpagewidth}{\paperwidth}
\setlength{\pdfpageheight}{\paperheight}
\begin{document}% FORMULA GOES INTO NEXT LINE, REPLACE EXISTING ONE
\(a^2+b^2=c^2\)
\end{document}