1. Find solution using graphical method
MAX z = 40x1 + 80x2
subject to
2x1 + 3x2 <= 48
x1 <= 15
x2 <= 10
and x1,x2 >= 0 Solution:Problem is MAX `z_x` | `=` | `` | `40` | `x_1` | ` + ` | `80` | `x_2` |
|
subject to |
`` | `2` | `x_1` | ` + ` | `3` | `x_2` | ≤ | `48` | `` | `` | `x_1` | | | | ≤ | `15` | | | | `` | `` | `x_2` | ≤ | `10` |
|
and `x_1,x_2 >= 0; ` |
Hint to draw constraints
1. To draw constraint `color{red}{2x_1+3x_2<=48 ->(1)}`
Treat it as `color{red}{2x_1+3x_2=48}`
When `x_1=0` then `x_2=?`
`=>2(0)+3x_2=48`
`=>3x_2=48`
`=>x_2=(48)/(3)=16`
When `x_2=0` then `x_1=?`
`=>2x_1+3(0)=48`
`=>2x_1=48`
`=>x_1=(48)/(2)=24`
2. To draw constraint `color{green}{x_1<=15 ->(2)}`
Treat it as `color{green}{x_1=15}`
Here line is parallel to Y-axis
3. To draw constraint `color{blue}{x_2<=10 ->(3)}`
Treat it as `color{blue}{x_2=10}`
Here line is parallel to X-axis
The value of the objective function at each of these extreme points is as follows:
Extreme Point Coordinates (`x_1`,`x_2`) | Lines through Extreme Point | Objective function value `z=40x_1 + 80x_2` |
`color{red}{O(0,0)}` | `color{black}{4->x_1>=0}` `color{black}{5->x_2>=0}` | `40(0)+80(0)=0` |
`color{green}{A(15,0)}` | `color{green}{2->x_1<=15}` `color{black}{5->x_2>=0}` | `40(15)+80(0)=600` |
`color{blue}{B(15,6)}` | `color{red}{1->2x_1+3x_2<=48}` `color{green}{2->x_1<=15}` | `40(15)+80(6)=1080` |
`color{brown}{C(9,10)}` | `color{red}{1->2x_1+3x_2<=48}` `color{blue}{3->x_2<=10}` | `40(9)+80(10)=1160` |
`color{darkorange}{D(0,10)}` | `color{blue}{3->x_2<=10}` `color{black}{4->x_1>=0}` | `40(0)+80(10)=800` |
The maximum value of the objective function `z=1160` occurs at the extreme point `(9,10)`.
Hence, the optimal solution to the given LP problem is : `x_1=9, x_2=10` and max `z=1160`.