所以互换x1与x4即用x,x来表示x2x12x2即: x3=3+2x4-x 2 x1=1-x4+x (7.7) 此时目标函数S=-19+4x4-x5所以互换 x1与x4 , 即用x4 , x5来表示x3 , x1 , x2 .即: x3 = 3 + 2x4 – x5 x1 = 1 – x4 + x5 (7.7) x2 = 3 – x5 此时目标函数 S´ = – 19 + 4x4 – x5      3 1 3 2