Border around text with page of full formulas

Question

I am trying to frame a text with \fbox and make auto-newline before or in the text. Currently, my formulas are out of the margin when they are too long (Sometimes there is text, not only formulas).

Part of my code :

\documentclass[a4paper]{article}
\usepackage[a4paper,top=0.1cm,bottom=0.1cm,left=0.1cm,right=1cm,marginparwidth=0.1cm]{geometry}
\usepackage{amsmath}

%boxx
\newcommand{\boxx}[1]{\fbox{#1}}
%matrix
\newcommand{\mtx}[2]{\ensuremath{{\binom{#1}{#2}}}}

\begin{document}
...
\boxx{$\mtx{n}{k} = \mtx n{n-k}$} 
\boxx{$\mtx{n}{k} = \frac nk \mtx{n-1}{k-1}$} 
\boxx{$\mtx{n}{k} = \mtx{n-1}{k-1} + \mtx{n-1}k$} 
\boxx{$\mtx{i}{k}\mtx{k}{j} = \mtx{i}{j} \mtx{i-j}{k-j}$} 
\boxx{$(x+y)^n = \sum^n_{k=0} \mtx nk x^{n-k}y^k$} 
\boxx{$\sum^m_{n=k}\mtx nk = \mtx{m+1}{k+1}$} 
\boxx{$(k_1,k_2,\dots,k_t) = \frac{n!}{k_1!k_2!\dots k_n!}$} 
\boxx{$(x_1+x_2+\dots+x_t)^n = \sum_{k_1+k2+\dots+k_t=n}(k_1,\dots,k_t) x_1^{k_1} , x_2^{k_2}, \dots, x_t^{k_t}$} 
\boxx{$(1+x)^n = \sum^n_{p=0}\mtx np x^n$}
\boxx{$(1+x)^{-n} = (\frac{1}{1-x})^n = \sum^n_{p=0}\mtx {n+q-1}q x^q$} 
...
\end{document}

Answer 1

I added \noindent\raggedright at the beginning of the document. The \noindent to prevent indentation on the 1st line, the \raggedright is useful when typesetting large horizontal blocks, which otherwise tend not to align with margins (if you did not want \raggedright, \sloppy might be an alternative, in which case the gaps would be distributed between boxes rather than at the end of the line).

No additional breaking mechanism is needed, because you provide an implied space between your \fboxes by putting one per line. If that space were absent, you would need an \allowbreak between \fboxes to permit the line break between boxes.

\documentclass[a4paper]{article}
\usepackage[a4paper,top=0.1cm,bottom=0.1cm,left=0.1cm,right=1cm,marginparwidth=0.1cm]{geometry}
\usepackage{amsmath}

%boxx
\newcommand{\boxx}[1]{\fbox{#1}}
%matrix
\newcommand{\mtx}[2]{\ensuremath{{\binom{#1}{#2}}}}

\begin{document}
\noindent\raggedright...
\boxx{$\mtx{n}{k} = \mtx n{n-k}$} 
\boxx{$\mtx{n}{k} = \frac nk \mtx{n-1}{k-1}$} 
\boxx{$\mtx{n}{k} = \mtx{n-1}{k-1} + \mtx{n-1}k$} 
\boxx{$\mtx{i}{k}\mtx{k}{j} = \mtx{i}{j} \mtx{i-j}{k-j}$} 
\boxx{$(x+y)^n = \sum^n_{k=0} \mtx nk x^{n-k}y^k$} 
\boxx{$\sum^m_{n=k}\mtx nk = \mtx{m+1}{k+1}$} 
\boxx{$(k_1,k_2,\dots,k_t) = \frac{n!}{k_1!k_2!\dots k_n!}$} 
\boxx{$(x_1+x_2+\dots+x_t)^n = \sum_{k_1+k2+\dots+k_t=n}(k_1,\dots,k_t) x_1^{k_1} , x_2^{k_2}, \dots, x_t^{k_t}$} 
\boxx{$(1+x)^n = \sum^n_{p=0}\mtx np x^n$}
\boxx{$(1+x)^{-n} = (\frac{1}{1-x})^n = \sum^n_{p=0}\mtx {n+q-1}q x^q$} 
...
\end{document}

Here is what it looks like with \raggedright replaced by \sloppy:

And here is what it would look like with \raggedright but \boxx defined as \newcommand{\boxx}[1]{\fbox{#1}\allowbreak\ignorespaces}