max 3x1 + x2
    sc
      x1 - x2 ≤ -1
    - x1 - x2 ≤ -3
     2x1 + x2 ≤ 4
       x1, x2 ≥ 0
    max 3x1 + x2
    sc
      x1 - x2 ≤ -1
    - x1 - x2 ≤ -3
     2x1 + x2 ≤ 2
       x1, x2 ≥ 0
    max 3x1 + x2
    sc
      x1 - x2 ≤ -1
    - x1 - x2 ≤ -3
     2x1 - x2 ≤ 2
       x1, x2 ≥ 0