\documentclass{minimal}
\usepackage[paperwidth=600pt,paperheight=450pt]{geometry}

\def\adjustdisplay#1 {
	\ifnum#1>0
		\newdimen\mydimen
		\mydimen\abovedisplayskip \abovedisplayskip\mydimen
		\mydimen\belowdisplayskip \belowdisplayskip\mydimen
	\fi
}

\def\foo{
	\vskip0.5ex
	\[\frac{x}{1} = \frac{1}{x-1}\]
	\vskip0.5ex
	\[x(x-1)=1\]
	\vskip0.5ex
	\[x^2-x=1\]
	\vskip0.5ex
	\[x^2-x-1=0\]
	\vskip0.5ex
	\[x=\frac{1+\sqrt{5}}{2},\frac{1-\sqrt{5}}{2}\]
}

\begin{document}

	\pagestyle{empty}
	\fontsize{20}{24}\selectfont
	\adjustdisplay{0}

	\foo

	\clearpage

	\foo\vskip0.5ex
	\[\phi = \frac{x}{1} = x =\frac{1+\sqrt{5}}{2} \approx 1.618\]

\end{document}
