[Tex/LaTex] How to “force” LaTeX to respect the page width

Question

In a document I write, I use the following for setting the page proportions:

\documentclass[12pt,a4paper]{report}
\setlength\textwidth{145mm}
\setlength\textheight{247mm}
\setlength\oddsidemargin{15mm}
\setlength\evensidemargin{15mm}
\setlength\topmargin{0mm}
\setlength\headsep{0mm}
\setlength\headheight{0mm}

However, sometimes I want certain blocks of text not to be broken into several lines.
In math mode, I use simply

 ${1+1+1=3}$

that is, composed brackets around the block. In normal text, I use

\mbox{crucial-expression}

However, in both cases, when the block comes inconveniently at the end of the line, it is often compiled so that the block exceeds the prescribed line width. I would like to force Latex somehow to put the block on the next line instead and stretch the preceding text to the whole line. In particular, I would rather not use \newline, because then the text on the upper line ends before the prescribed line width.

(Moreover, I would like to do it in a way that dos not change the above setting of the page proportions, if possible.)

I am sorry if this is a duplicate of some sort, I was not able to find anything related here (maybe because of my poor terminology concerning typing).

Thanks in advance for any tips.

Answer 1

As noted in comments, using \sloppy or the sloppypar environment (or as an alternative setting \setlength\emergencystretch\textwidth) allow TeX to favour stretching white space to keep text within margins where possible.