\documentclass[11pt,leqno,fleqn]{book}
\input 600-spring2015.sty
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%\textheight 600pt
\def\Rbar{\overline \RR}
\begin{document}
\Heading
The extended real line
\endHeading
%Homework Problem 1.5 was an inelegant attempt to convince you that
%$\bb[0,\infty]$ is quite similar to $\bb[0,\infty)$, with only a few
%minor changes involving~$\infty$.
%Let me start again.
%
For the purpose of limit operations it is convenient to compactify the real line by the addition of two new points:
$\Rbar=\RR\cup\{-\infty\}\cup\{+\infty\}$. The ordering of~$\RR$ is extended
to~$\Rbar$ by specifying that~$-\infty