How do I suppress the whitespace above the equation block at the page top ?
It is added to the top margin, and I don't want that to happen.
I know that \abovedisplayshortskip controls this for the whole document, but how can I change this for this particular equation block and NOT for any others ?
Negative vspace doesn't work.
\documentclass[pdftex,12pt,a4paper,english,dutch,leqno]{article}
\usepackage[top=1cm,right=1cm,bottom=1cm,left=1.5cm,noheadfoot]{geometry}
\usepackage{babel}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{empheq}
\begin{document}
\abovedisplayskip=6pt
\abovedisplayshortskip=3pt % This should NOT be changed
\belowdisplayskip=6pt
\belowdisplayshortskip=3pt
\begin{equation*}
\left.\begin{array}{r}
a_{31}'=a_{11}\cdot a_{31}-a_{31}\cdot a_{11}=0\\
a_{32}'=a_{11}\cdot a_{32}-a_{31}\cdot a_{12}\\
a_{33}'=a_{11}\cdot a_{33}-a_{31}\cdot a_{13}\\
a_{34}'=a_{11}\cdot a_{34}-a_{31}\cdot a_{14}\\
b_{3}'=a_{11}\cdot b_{3}-a_{31}\cdot b_{1}
\end{array}\!\!\right\}
\Longrightarrow\;
\begin{matrix*}[l]
\text{Pseudo-code :}\\
a_{11}\cdot b_{3}-a_{31}\cdot b_{1}\mapsto b_{3}\text{.}\\
\forall\;i\in\{4,3,2,1\} : a_{11}\cdot a_{3i}-a_{31}\cdot a_{1i}\mapsto a_{3i}\text{.} \end{matrix*}
\end{equation*}
\end{document}
Best Answer
It is not a skip that you have above the equation but a one line paragraph consisting of an indentation box and parfillskip glue. TeX display math environments do not generally react well to starting a paragraph they are designed to work mid-paragraph. If you need to do this you need to suppress the paragraph start with
and you will see the equation move up the page.