Linear Programming 855D98
1. **State the problem:**
We want to maximize the objective function $$Z = 2x_1 + 10x_2$$
subject to the constraints:
$$10x_1 + 4x_2 \geq 40$$
$$x_1 + 6x_2 \geq 24$$
$$x_1 + 2x_2 \leq 14$$
with $$x_1, x_2 \geq 0$$.
2. **Rewrite inequalities for clarity:**
- Labor: $$10x_1 + 4x_2 \geq 40$$
- Material: $$x_1 + 6x_2 \geq 24$$
- Storage: $$x_1 + 2x_2 \leq 14$$
- Non-negativity: $$x_1 \geq 0, x_2 \geq 0$$
3. **Convert inequalities to equalities to find boundary lines:**
- Labor line: $$10x_1 + 4x_2 = 40$$
- Material line: $$x_1 + 6x_2 = 24$$
- Storage line: $$x_1 + 2x_2 = 14$$
4. **Find intersection points of constraints to identify feasible region vertices:**
- Intersection of Labor and Material:
Solve system:
$$10x_1 + 4x_2 = 40$$
$$x_1 + 6x_2 = 24$$
From second: $$x_1 = 24 - 6x_2$$
Substitute into first:
$$10(24 - 6x_2) + 4x_2 = 40 \Rightarrow 240 - 60x_2 + 4x_2 = 40$$
$$-56x_2 = -200 \Rightarrow x_2 = \frac{200}{56} = \frac{25}{7} \approx 3.571$$
Then $$x_1 = 24 - 6 \times 3.571 = 24 - 21.429 = 2.571$$
- Intersection of Labor and Storage:
$$10x_1 + 4x_2 = 40$$
$$x_1 + 2x_2 = 14$$
From second: $$x_1 = 14 - 2x_2$$
Substitute:
$$10(14 - 2x_2) + 4x_2 = 40 \Rightarrow 140 - 20x_2 + 4x_2 = 40$$
$$-16x_2 = -100 \Rightarrow x_2 = \frac{100}{16} = 6.25$$
Then $$x_1 = 14 - 2 \times 6.25 = 14 - 12.5 = 1.5$$
- Intersection of Material and Storage:
$$x_1 + 6x_2 = 24$$
$$x_1 + 2x_2 = 14$$
Subtract second from first:
$$(x_1 + 6x_2) - (x_1 + 2x_2) = 24 - 14 \Rightarrow 4x_2 = 10 \Rightarrow x_2 = 2.5$$
Then $$x_1 = 14 - 2 \times 2.5 = 14 - 5 = 9$$
5. **Check which intersection points satisfy all constraints:**
- Point A: $$(2.571, 3.571)$$
Check Storage: $$2.571 + 2 \times 3.571 = 2.571 + 7.142 = 9.713 \leq 14$$ (valid)
- Point B: $$(1.5, 6.25)$$
Check Material: $$1.5 + 6 \times 6.25 = 1.5 + 37.5 = 39 > 24$$ (valid)
- Point C: $$(9, 2.5)$$
Check Labor: $$10 \times 9 + 4 \times 2.5 = 90 + 10 = 100 > 40$$ (valid)
6. **Evaluate objective function at each vertex:**
- At A: $$Z = 2(2.571) + 10(3.571) = 5.142 + 35.71 = 40.852$$
- At B: $$Z = 2(1.5) + 10(6.25) = 3 + 62.5 = 65.5$$
- At C: $$Z = 2(9) + 10(2.5) = 18 + 25 = 43$$
7. **Check corner points on axes (if feasible):**
- At $$x_1=0$$:
Labor: $$4x_2 \geq 40 \Rightarrow x_2 \geq 10$$
Material: $$6x_2 \geq 24 \Rightarrow x_2 \geq 4$$
Storage: $$2x_2 \leq 14 \Rightarrow x_2 \leq 7$$
No $$x_2$$ satisfies both $$x_2 \geq 10$$ and $$x_2 \leq 7$$, so no feasible point at $$x_1=0$$.
- At $$x_2=0$$:
Labor: $$10x_1 \geq 40 \Rightarrow x_1 \geq 4$$
Material: $$x_1 \geq 24$$
Storage: $$x_1 \leq 14$$
No $$x_1$$ satisfies both $$x_1 \geq 24$$ and $$x_1 \leq 14$$, so no feasible point at $$x_2=0$$.
8. **Conclusion:**
The maximum value of $$Z$$ is at point B: $$(1.5, 6.25)$$ with $$Z = 65.5$$.
**Final answer:** $$\boxed{\max Z = 65.5 \text{ at } (x_1, x_2) = (1.5, 6.25)}$$