Hello,
I do not succeed in having two sub-columns of the same width in the third
column.
Thank you.
Fabrice

\useMPlibrary[dum]
\startsetups[table:initialize]

  \setupTABLE[start][align={middle,lohi},offset=0.8ex]
  \setupTABLE[column][2][width=0.5\textwidth]
  \setupTABLE[column][3][width=0.4\textwidth]
  \setupTABLE[column][first][width=1.5cm]
  \setupTABLE[1][1,2,3][frame=off]

\stopsetups

\starttext

\startlinecorrection[blank]
\startmidaligned
\bTABLE[setups=table:initialize]

\bTR
  \bTD                \eTD
  \bTD Algébriquement \eTD
  \bTD [nc=2] Graphiquement  \eTD
\eTR
\bTR
 \bTD                                                 \eTD
 \bTD[nr=2] L'équation \math{ax^2+bx+c=0}             \eTD
 \bTD[nc=2] La parabole d'équation \math{y=ax^2+bx+c} \eTD
\eTR
\bTR
 \bTD                                                 \eTD
 \bTD Cas où \math{a\geqslant 0}                      \eTD
 \bTD Cas où \math{a\leqslant 0}                      \eTD
\eTR
\bTR
 \bTD    \math{\Delta >0}                             \eTD
 \bTD  admet deux solutions distinctes :
            \startformula
 x_1=\frac{-b-\sqrt{\Delta}}{2a}\quad \rm{et} \quad
x_2=\frac{-b+\sqrt{\Delta}}{2a}
            \stopformula
\eTD
\bTD[nc=2] coupe deux fois l'axe des abscisses
\dontleavehmode\startcombination[2*1]{\externalfigure[dummy][scale=900]}{}{\externalfigure[dummy][scale=900]}{}
\stopcombination \eTD
\eTR
\bTR
 \bTD    \math{\Delta=0}                             \eTD
 \bTD  admet une unique solution :
            \startformula
               x_0=-\frac{b}{2a}
            \stopformula
\eTD
\bTD[nc=2] coupe l'axe des abscisses en un seul point
\dontleavehmode\startcombination[2*1]{\externalfigure[dummy][scale=900]}{}{\externalfigure[dummy][scale=900]}{}
\stopcombination \eTD
\eTR
\bTR
 \bTD    \math{\Delta<0}                             \eTD
 \bTD  n'admet pas de solution
\eTD
\bTD [nc=2] ne coupe pas l'axe des abscisses
\dontleavehmode\startcombination[2*1]{\externalfigure[dummy][scale=900]}{}{\externalfigure[dummy][scale=900]}{}
\stopcombination        \eTD
\eTR
\eTABLE

\stopmidaligned
\stoplinecorrection

\stoptext