今天试着用linprog函数解张伯生版运筹学第一章“飞乐公司”那个案例。
目标函数：maxZ=-15x1+25x2+15x3+-30x4+10x5-40x7-10x9
约束条件：-0.5x1+0.5x2+0.5x3<=0
-0.25x1+0.75x2-0.25x3<=0
-0.75x4+0.25x5-0.25x6<=0
-0.5x4+0.5x5-0.5x6<=0
x1+x4+x7<=100
x2+x5+x8<=100
x3+x6+x9<=60
x1……x9>=0
我写的代码：
c=[-15;25;15;-30;10;0;-40;0;-10];
a=[-0.5,0.5,0.5,0,0,0,0,0,0;
     -0.25,0.75,-0.25,0,0,0,0,0,0;
     0,0,0,-0.75,0.25,0.25,0,0,0;
     0,0,0,-0.5,0.5,-0.5,0,0,0;
     1,0,0,1,0,0,1,0,0;
     0,1,0,0,1,0,0,1,0;
     0,0,1,0,0,1,0,0,1];
b=[0;0;0;0;100;100;60];
[x,fval]=linprog(-c,a,b,[],[],zeros(9,1))
输出结果是：
x =
  100.0000
   50.0000
   50.0000
    0.0000
    0.0000
    0.0000
    0.0000
   25.0000
    0.0000
fval = -500.0000
结果是总利润，不应该是负的啊。书上结果是3400。请教一下我是哪儿出错了？