documentclass{article}
usepackage{tikz}
begin{document}
usetikzlibrary{matrix}
% The table environment:
newenvironment{matrixtable}[3]{%
  begin{tikzpicture}[matrix of nodes/.style={
    execute at begin cell=nodebgroupstrut,
    execute at end cell=egroup;}]
  matrix (m) [matrix of nodes,top color=white!20,
    bottom color=white!80,draw=white,
    nodes={draw,top color=white!10,bottom color=blue!15,
    draw,inner sep=2pt,minimum height=3.1ex},
    column sep=1ex,row sep=0.6ex,inner sep=2ex,
    rounded corners,column 1/.style={minimum width=#1},
    column 2/.style={minimum width=#2},
    column 3/.style={minimum width=#3}]}
   %
{;end{tikzpicture}}
%


begin{center}
begin{frame}

begin{matrixtable}{7cm}{3cm}{7cm}{
  head{Intervalle}   & head{Inégalité} & head{Représentation graphique}  \
  $[a~;~b]text{ fermé }$ & $ ale xle b$  & graph 1 \
  $[a~;~b[text{ fermé à  gauche, ouvert à  droite }$ & $ale x<b $   & graph2 \
  $]a~;~b]text{ ouvert à gauche, fermé à droite }$ & $a<xle b$      & graph3\
   $]a~;+infty [$ & $x>a$ &  graph4 \
  $[a~;+infty [$ & $xge a$ &  graph5  \
 $]-infty;b~ [$ & $x< b$ &  graph6    \
  $]-infty;b~ ]$ & $xle b$ &  graph7     \
  }
end{matrixtable}

end{frame}
end{center}
end{document}

usepackage{tikz}
usetikzlibrary{arrows.meta,decorations.pathreplacing}
begin{document}
begin{tikzpicture}
 draw[stealth-stealth] (-6,0) node[below]{$-infty$} -- (6,0) node[below]{$infty$};
 draw[very thick,blue,{Bracket[reversed,width=1.2em]}-{Bracket[width=1.2em]}] (-3.05,0) -- (2,0) node[pos=-1/40,above]{$a$} node[pos=29/30,above]{$b$};
 end{tikzpicture}
end{document}