Big M Minimization
1. **State the problem:** Minimize the objective function $$Z = 4x + 3y$$ subject to the constraints:
$$2x + y \geq 10$$
$$3x + 2y \leq 6$$
$$x + y \geq 6$$
$$x, y \geq 0$$
2. **Convert inequalities to equalities using slack, surplus, and artificial variables:**
For $$2x + y \geq 10$$, rewrite as $$2x + y - s_1 = 10$$ with surplus variable $$s_1 \geq 0$$ and add artificial variable $$a_1$$:
$$2x + y - s_1 + a_1 = 10$$
For $$3x + 2y \leq 6$$, add slack variable $$s_2$$:
$$3x + 2y + s_2 = 6$$
For $$x + y \geq 6$$, rewrite as $$x + y - s_3 = 6$$ with surplus variable $$s_3 \geq 0$$ and add artificial variable $$a_2$$:
$$x + y - s_3 + a_2 = 6$$
3. **Set up the Big-M objective function:**
Introduce a large positive number $$M$$ and penalize artificial variables:
$$Z = 4x + 3y + M a_1 + M a_2$$
4. **Formulate the initial simplex tableau with variables $$x, y, s_1, s_2, s_3, a_1, a_2$$ and constraints:**
$$\begin{cases}
2x + y - s_1 + a_1 = 10 \\
3x + 2y + s_2 = 6 \\
x + y - s_3 + a_2 = 6
\end{cases}$$
5. **Apply the simplex method to minimize $$Z$$:**
- Start with artificial variables $$a_1$$ and $$a_2$$ in the basis.
- Perform pivot operations to remove artificial variables from the basis.
- Continue iterations until no negative coefficients remain in the objective row.
6. **Solve the system or use software to find the optimal solution:**
After applying the Big-M method and simplex iterations, the optimal solution is:
$$x = 0, y = 3, Z = 4(0) + 3(3) = 9$$
7. **Verify constraints:**
- $$2(0) + 3 = 3 \geq 10$$? No, so this solution is infeasible.
Re-examining constraints and calculations, the problem is infeasible because constraints $$2x + y \geq 10$$ and $$3x + 2y \leq 6$$ cannot be satisfied simultaneously with $$x, y \geq 0$$.
**Final conclusion:** The problem has no feasible solution under the given constraints.