Reduce white space before and after multicols environment

Question

I wonder how to reduce the vertical space before and after a multicols environment. I have something like below

\begin{multicols}{3}
   {
      \begin{equation}\sum F_x = 0\end{equation}
      \begin{equation}\frac{dP}{dx} - p = 0\end{equation}
   }
   {
      \begin{equation}\sum F_y = 0\end{equation}
      \begin{equation}\frac{dQ}{dx} + q = 0\end{equation}
   }
   {
      \begin{equation}\sum M = 0\end{equation}
      \begin{equation}\frac{dQ}{dx} + q = 0\end{equation}
   }
\end{multicols}

But there is extra white space before and after the multicols environment. How can I reduce it?

Answer 1

While I wouldn't recommend it normally, you can also fiddle with the \multicolsep length.

\documentclass{article}
\usepackage{multicol}
\setlength{\multicolsep}{6.0pt plus 2.0pt minus 1.5pt}% 50% of original values
\usepackage{lipsum}

\begin{document}
\lipsum[1]
\begin{multicols}{3}
   \noindent
   \begin{equation}\sum F_x = 0\end{equation}
   \begin{equation}\frac{dP}{dx} - p = 0\end{equation}
   \begin{equation}\sum F_y = 0\end{equation}
   \begin{equation}\frac{dQ}{dx} + q = 0\end{equation}
   \begin{equation}\sum M = 0\end{equation}
   \begin{equation}\frac{dQ}{dx} + q = 0\end{equation}
\end{multicols}
\lipsum[1]
\end{document}

Answer 2

I would consider some of the other ways to do alignment, but if you want to use multicol, you need to add \noindent:

\documentclass{article}
\usepackage{multicol}
\usepackage{lipsum}

\begin{document}
\lipsum[1]
\begin{multicols}{3}
   \noindent
   \begin{equation}\sum F_x = 0\end{equation}
   \begin{equation}\frac{dP}{dx} - p = 0\end{equation}
   \begin{equation}\sum F_y = 0\end{equation}
   \begin{equation}\frac{dQ}{dx} + q = 0\end{equation}
   \begin{equation}\sum M = 0\end{equation}
   \begin{equation}\frac{dQ}{dx} + q = 0\end{equation}
\end{multicols}
\lipsum[1]
\end{document}