equ21(a, b, c)

           function x  = equ21(a, b, c)

           if nargin < 2
             error('Pas assez de paramtres');
           if nargin == 2
             x = equ1(a, b);
           elseif a == 0;
              x = equ1(b, c);
           else
              delta = b*b-4*a*c;
              if delta >= 0
                 if b > 0
                    x = (-b-sqrt(delta))/(2*a);
                 else
                    x = (-b+sqrt(delta))/(2*a); 
                 end;
                 if x == 0
                    x = [x 0];
                 else
                    x = [x (c/a)/x];
                 end;
              end;                 
           end;