\documentclass[10pt,a4paper]{article}
\usepackage[utf8x]{inputenc}
\usepackage{ucs}
\usepackage[francais]{babel}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage[left=2cm,right=2cm,top=2cm,bottom=2cm]{geometry}
\author{Mamouni My Ismail}
\newcommand{\R}{\mathbb{R}}
\newcommand{\N}{\mathbb{N}}
\newcommand{\Z}{\mathbb{Z}}
\newcommand{\Q}{\mathbb{Q}}
\newcommand{\intg}{\int_a^bf(t)dt}
\newcommand{\ab}{aaaaaaaaaaaaaaaaaaa yuuuuuuuuuu poiiiiiiii ghhhh}
\newcommand{\norme}[1]{\Vert #1\Vert}
\newcommand{\matrice}[2]{\begin{pmatrix}
#1 & 0 \\ 
2 & #2
\end{pmatrix} }
\newcommand{\ds}{\displaystyle}
\newcommand{\somme}[3]{\sum_{#1}^{#2}{#3}}
\newcommand{\vers}{\longrightarrow}
\newcommand{\versA}{\longmapsto}
\newcommand{\app}[5]{
\begin{array}{cccc}
#1: & #2 & \vers & #3 \\ 
 & #4 & \versA & #5
\end{array} 
}
\begin{document}
\begin{center}
\textbf{Niveau élémentaire : TP 3}

\textbf{Personnaliser \LaTeX}
\end{center}

\begin{itemize}
\item \textbf{Matrices} : 
$\matrice{a}{b}$

$\matrice{\frac{\ln(a)}{1+b}}{\frac{b^2-2b}{a^2+2}}$
\item \textbf{Sommes} : $\ds\somme{k=0}{n}{x_k^2}$

$\somme{k=0}{n}{x_k^2}$

$\somme{k=3}{n^2}{\frac{1}{2^k}}$

$\ds\somme{k=3}{n^2}{\frac{1}{2^k}}$
\item \textbf{Applications :} $$\begin{array}{cccc}
f: & \R & \vers & \R \\ 
 & x & \versA & x^2
\end{array} $$

$$
\app{g}{\Q}{\Z}{t}{E(t)}
$$
\item \textbf{Integrales, ...}
\end{itemize}





\end{document}