# Displaying multiple equations

I want to display multiple lines of centered equations. Each equation has multiple equalities and inequalities, so aligning is not called for. All I want is display them one line at a time, centered, with not too much space between them. Is the only way to use multiple \begin{equation}\end{equation} environments? Surely there must be a more efficient way, but I can't seem to find any way to do this online. Here is an example:

$$(a_1,\ldots,a_n)M\subset(a_1,\ldots,a_{n+m})M\subsetneq M,$$
$$(a_{n+1},\ldots,a_{n+m})\frac{M}{(a_1,\ldots,a_n)M}\simeq\frac{(a_1,\ldots,a_{n+m})M}{(a_1,\ldots,a_n)M}\subsetneq\frac{M}{(a_1,\ldots,a_n)M}.$$

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Hint: You can replace \ldots by \dots and let TeX take care of the placement. –  Svend Tveskæg Aug 21 at 0:40

You are already using amssymb I hope. Why not look in to the amsmath manual (texdoc amsldoc from command prompt/line). It provides many environments for typing mathematics. For these two equations, you can use gather* (no number).

\documentclass[11pt,openany]{book}
\usepackage{amsmath,amssymb,showframe}   %% showframe for demo only
\begin{document}
\begin{gather*}
(a_1,\ldots,a_n)M\subset(a_1,\ldots,a_{n+m})M\subsetneq M,\\
(a_{n+1},\ldots,a_{n+m})\frac{M}{(a_1,\ldots,a_n)M}\simeq
\frac{(a_1,\ldots,a_{n+m})M}{(a_1,\ldots,a_n)M}\subsetneq\frac{M}{(a_1,\ldots,a_n)M}.
\end{gather*}
\end{document}


If you have long equations, then you may even prefer multline environment. If you use mathtools package instead, it will load amsmath by itself along with extended macros.

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