A = [-0.2   -1.8    3.9   -6.0   -1.6
    6.3    8.0    3.0    2.5    5.1
   -0.8   -9.9    9.7    4.7    5.9
   -0.9   -4.1    1.1   -2.5    8.0
   -1.0   -9.0   -2.0   -9.8    6.9]

x = [-2.6
      2.4
      4.6
     -6.1
      8.1]


