
 * Solve this system :                                 (cb1.c)

 2/1  2/1 -1/1  0/1  1/1 0/1
-1/1 -1/1  2/1 -3/1  1/1 0/1
 1/1  1/1 -2/1  0/1 -1/1 0/1
 0/1  0/1  1/1  1/1  1/1 0/1

 * The gaussjordanF() function give :

  1/1  1/1  0/1  0/1  1/1  0/1
  0/1  0/1  1/1  0/1  1/1  0/1
  0/1  0/1  0/1  1/1  0/1  0/1
  0/1  0/1  0/1  0/1  0/1  0/1   < zero row


 * Eliminate the zero row.                              (cb2.c) 
 * The leading variables are (pivot = 1) :
  
   x1          x3    x4

 [1/1] 1/1  0/1  0/1  1/1  0/1
  0/1  0/1 [1/1] 0/1  1/1  0/1
  0/1  0/1  0/1 [1/1] 0/1  0/1

  
 * The  free  variables  are (pivot = 0) :
  
        x2                 x5           
  
  1/1  1/1  0/1  0/1  1/1  0/1     
  0/1 [0/1] 0/1  0/1  0/1  0/1    
  0/1  0/1  1/1  0/1  1/1  0/1    
  0/1  0/1  0/1  1/1  0/1  0/1    
  0/1  0/1  0/1  0/1 [0/1] 0/1     

  * We assign a value at the free variables : 

        x2=s              x5=t         
                                   s       t 
  1/1  1/1  0/1  0/1  1/1  0/1      
  0/1 [1/1] 0/1  0/1  0/1  0/1    [1/1]  
  0/1  0/1  1/1  0/1  1/1  0/1      
  0/1  0/1  0/1  1/1  0/1  0/1     
  0/1  0/1  0/1  0/1 [1/1] 0/1           [1/1]



  * Now you can compute the general solution :

  1/1  1/1  0/1  0/1  1/1  0/1     0/1     0/1
  0/1  1/1  0/1  0/1  0/1  0/1     1/1     0/1
  0/1  0/1  1/1  0/1  1/1  0/1     0/1     0/1
  0/1  0/1  0/1  1/1  0/1  0/1     0/1     0/1
  0/1  0/1  0/1  0/1  1/1  0/1     0/1     1/1
