 A = [ 4  0  -3   2  4 
       2  8  -4  -1  3 
      -1  2   1  10 -2 
       4  4  -2   1  2 
      -2  3   1   1 -1]

x = [ 1
      3
     -2
      3
     -1]

y = [ 2
      0
     13
     -2
      1]

c = -13


