\documentclass[12pt] {article} \usepackage[T1]{fontenc} 
\usepackage[utf8]{inputenc}
\usepackage{amsmath,amssymb,graphicx,multicol,mathrsfs, fancyhdr,enumerate,fourier,eurosym,enumerate,tabularx,variations,numprint}
\usepackage[dvips]{color}
\usepackage[tikz]{bclogo}
\usepackage{pst-plot,pst-tree,pstricks,pst-node,pstricks-add,pst-math,pst-xkey,pst-eucl}
\usepackage[francais]{babel} 
\everymath{\displaystyle}
%\usepackage[colorlinks=true,pdfstartview=FitV,linkcolor=blue,citecolor=blue,urlcolor=blue]{hyperref}
\textwidth 19cm \textheight 24cm \hoffset 
-1,4cm \voffset -3.7cm \oddsidemargin 0pt 
\renewcommand{\thesubsection}{\textcolor{blue}{\Roman{subsection}}} 
\renewcommand{\thesubsubsection}{\textcolor{blue}{\Roman{subsection}}.\textcolor{blue}{\arabic{subsubsection}}} 
\pagestyle{empty}
% pour le pied de page central
\cfoot{Page \thepage/\pageref{fin}}

\begin{document}
%\tableofcontents

\begin{center}\section*{\textcolor{red}{Correction des exercices de développement}}\end{center}


\begin{enumerate}[$A(x)=$]

\item 	$2x(-7x+4)=\boxed{\textcolor{red}{-14x^2+8x}}$

\bigskip

\item $3(6x-8)-(-9-6x)=18x-24+9+6x=\boxed{\textcolor{red}{24x-15}}$

\bigskip
	
\item $4x+2(-2x+3)=4x-4x+6=6$

\bigskip

\item $3+(-9x+5)(4x+7)=3+\left[-36x^2-63x+20x+35\right]=3-36x^2-63x+20x+35=\boxed{\textcolor{red}{-36x^2-43x+38}}$

\bigskip

\item $(3x+2)(-6x-7)=-18x^2-21x-12x-14=\boxed{\textcolor{red}{-18x^2-33x-14}}$

\bigskip

\item $(3x+5)(7x-2)-(9x+2)(3x-8)=\left[21x^2-6x+35x-10\right]-\left[27x^2-72x+6x-16\right]\\
=\left[21x^2+29x-10\right]-\left[27x^2-66x-16\right]\\
=21x^2+29x-10-27x^2+66x+16=\boxed{\textcolor{red}{-6x^2+95x+6}}$
\end{enumerate}

\label{fin}
\end{document}  