求z=3x1-x2-x3的最大值其中x1-2x2+x3<=11,-4x1+x2+2x3>=3,-2x2+x3=1,同时x1、x2、x3都大于等于零
时间: 2023-10-01 15:11:34 浏览: 192
求3个整数中的最大值
这是一个线性规划问题,我们可以使用单纯性法求解。
将约束条件和目标函数写成矩阵形式:
```
max z = [3 -1 -1] [x1]
[x2]
[x3]
subject to:
[ 1 -2 1] [x1] <= 11
[-4 1 2] [x2] >= 3
[ 0 -2 1] [x3] = 1
x1 ≥ 0, x2 ≥ 0, x3 ≥ 0
```
将不等式约束转化为等式约束:
```
x1 - 2x2 + x3 + x4 = 11
-4x1 + x2 + 2x3 - x5 = -3
-2x2 + x3 + x6 = 1
```
将目标函数和约束条件写成增广矩阵形式:
```
[ 3 -1 -1 0 0 0 0] [x1] [ 0]
[ 1 -2 1 1 0 0 0] [x2] [11]
[-4 1 2 0 -1 0 0] [x3] = [-3]
[ 0 0 1 0 0 1 0] [x4] [ 0]
[ 0 0 2 0 0 0 -1] [x5] [ 3]
[ 0 -2 1 0 0 0 1] [x6] [ 1]
```
使用单纯性法解出最优解:
```
[ 3 -1 -1 0 0 0 0] [x1] [ 0]
[ 1 -2 1 1 0 0 0] [x2] [11]
[-4 1 2 0 -1 0 0] [x3] = [-3]
[ 0 0 1 0 0 1 0] [x4] [ 0]
[ 0 0 2 0 0 0 -1] [x5] [ 3]
[ 0 -2 1 0 0 0 1] [x6] [ 1]
pivot at (2, 2)
[ 3 -1 -1 0 0 0 0] [x1] [ 7]
[ 0 -3 2 1 0 0 0] [x2] [ 18]
[ 0 -3 6 0 -1 0 0] [x3] = [ -33]
[ 0 0 1 0 0 1 0] [x4] [ 0]
[ 0 0 0 0 0 -2 1] [x5] [ 9]
[ 0 0 3 0 0 0 1] [x6] [ 12]
pivot at (2, 3)
[ 3 -1 -1 0 0 0 0] [x1] [ 4.5]
[ 0 -3 2 1 0 0 0] [x2] [ 6.5]
[ 0 0 4 3 -1 0 0] [x3] = [-4.5]
[ 0 0 1 0 0 1 0] [x4] [ 0]
[ 0 0 0 0 0 -2 1] [x5] [ 9]
[ 0 0 3 0 0 0 1] [x6] [ 12]
pivot at (3, 4)
[ 3 -1 -1 0 0 0 0] [x1] [ 4.5]
[ 0 -3 0 1 1 0 0] [x2] [ 7.5]
[ 0 0 4 3 -1 0 0] [x3] = [-4.5]
[ 0 0 1 0 0 1 0] [x4] [ 0]
[ 0 0 0 0 0 -2 1] [x5] [ 9]
[ 0 0 0 -3 3 0 1] [x6] [ 12]
pivot at (2, 5)
[ 3 -1 -1 0 0 0 0] [x1] [ 7]
[ 0 -3 0 1 1 0 0] [x2] [ 7.5]
[ 0 1 4 3 -3 0 0] [x3] = [ 4.5]
[ 0 0 1 0 0 1 0] [x4] [ 0]
[ 0 0 0 0 -2 -2 1] [x5] [ -9]
[ 0 0 0 -3 3 0 1] [x6] [ 12]
pivot at (1, 3)
[ 3 0 -2 1 1 0 0] [x1] [ 9]
[ 0 -3 0 1 1 0 0] [x2] [ 7.5]
[ 0 1 4 3 -3 0 0] [x3] = [ 4.5]
[ 0 0 1 0 0 1 0] [x4] [ 0]
[ 0 0 0 0 -2 -2 1] [x5] [ -9]
[ 0 0 0 -3 3 0 1] [x6] [ 12]
pivot at (3, 2)
[ 3 0 0 4 -2 0 0] [x1] [ 18]
[ 0 -3 0 1 1 0 0] [x2] [ 7.5]
[ 0 1 1 -1 1 0 0] [x3] = [ 1.5]
[ 0 0 1 0 0 1 0] [x4] [ 0]
[ 0 0 0 0 -2 -2 1] [x5] [ -9]
[ 0 0 0 -3 3 0 1] [x6] [ 12]
pivot at (3, 3)
[ 3 0 0 4 -2 0 0] [x1] [ 18]
[ 0 -3 0 1 1 0 0] [x2] [ 7.5]
[ 0 1 1 -1 1 0 0] [x3] = [ 1.5]
[ 0 0 1 0 0 1 0] [x4] [ 0]
[ 0 0 0 0 -2 -2 1] [x5] [ -9]
[ 0 0 0 -3 3 0 1] [x6] [ 12]
最优解为:x1=18, x2=0, x3=1.5,最大值为z=3x1-x2-x3=54.5。
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