too much vertical space after tabularx with equations

Question

I am attempting to use tabularx to put multiple numbered equations on the same line, as suggested in this answer.

MWE 1:

\documentclass{article}
\usepackage{tabularx}
\begin{document}
blah blah text

\noindent\begin{tabularx}{\linewidth}{@{}XX@{}}
\begin{equation}
1+1+2
\end{equation}
&
\begin{equation}
2+2=4
\end{equation}
\end{tabularx}
%
blah blah text
\end{document}

This produces

MWE 2:

\documentclass{article}
\usepackage{tabularx}
\begin{document}
blah blah text

\noindent\begin{tabularx}{\linewidth}{@{}XX@{}}
asdfasfd
&
asfdasdf
\end{tabularx}
%
blah blah text
\end{document}

This produces

MWE 2 is fine, the spacing is the same on the top and the bottom. What gives for MWE 1 though? How do I get it such that the spacing before and after the tabularx environment is the same as what I would normally get from an equation environment?

Answer 1

To economize drastically on (vertical) whitespace, you could encase the equation environments in minipage environments (of width \hsize). Alternatively, don't use equation environments at all; instead, use low-level code to display the math material, to increment the equation counter, and to display the equation number.

\documentclass{article}
\usepackage{tabularx}
\begin{document}

\hrule
\noindent%
\begin{tabularx}{\linewidth}{@{}XX@{}}
\begin{minipage}{\hsize}
\begin{equation}
1+1+2
\end{equation}
\end{minipage}
&
\begin{minipage}{\hsize}
\begin{equation}
2+2=4
\end{equation}
\end{minipage}
\end{tabularx}
\hrule

\bigskip
\hrule
\noindent%
\begin{tabularx}{\linewidth}{@{}XX@{}}
\hfill$\displaystyle 1+1=2$\hfill
\refstepcounter{equation}(\theequation)
&
\hfill$\displaystyle 2+2=4$\hfill
\refstepcounter{equation}(\theequation)
\end{tabularx}
\hrule

\bigskip
\hrule
\noindent
\begin{tabularx}{\linewidth}{@{}XX@{}}
asdfasfd & asfdasdf
\end{tabularx}
\hrule

\end{document}

Answer 2

You can (locally) set the spacing parameters above and below displays to zero.

It's easier if you also define a proper environment. If you need consecutive equation environments (but you shouldn't), use the shown trick.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tabularx}
\usepackage{environ}

\usepackage{lipsum}% just for the example

\newlength{\savedbdss}
\NewEnviron{multieq}[1]{%
  \[
  \begin{minipage}{\displaywidth}
  \setlength{\savedbdss}{\belowdisplayshortskip}
  \setlength{\abovedisplayshortskip}{0pt}%
  \setlength{\belowdisplayshortskip}{0pt}%
  \begin{tabularx}{\displaywidth}{@{}*{#1}{>{\noindent\vspace*{-\baselineskip}}X}@{}}
  \BODY
  \end{tabularx}
  \vspace{-\belowdisplayskip}
  \vspace{-\savedbdss}
  \end{minipage}
  \]
}

\begin{document}

\lipsum[1][1-4]
\begin{multieq}{2}
\begin{equation}
1+1+2
\end{equation}
&
\begin{equation}
2+2=4
\end{equation}
\end{multieq}
\lipsum[2][1-3]
\begin{multieq}{2}
\begin{equation}
1+1+2
\end{equation}
&
\begin{equation}
2+2=4
\end{equation}
\\[-\savedbdss]
\begin{equation}
1+1+2
\end{equation}
&
\begin{equation}
2+2=4
\end{equation}
\end{multieq}
\lipsum[2][1-3]

\end{document}