1. **State the problem:** Maximize the objective function $$P = 2x_1 + 5x_2$$ subject to the constraint $$-2x_1 + x_2 \leq 8$$ and $$x_1, x_2 \geq 0$$.
2. **Set up the problem for the simplex method:**
Rewrite the constraint as $$-2x_1 + x_2 + s = 8$$ where $$s \geq 0$$ is the slack variable.
3. **Initial simplex tableau:**
\[
\begin{array}{c|ccc|c}
& x_1 & x_2 & s & RHS \\
\hline
s & -2 & 1 & 1 & 8 \\
P & -2 & -5 & 0 & 0 \\
\end{array}
\]
4. **Simplex method steps:**
- Identify entering variable: most negative coefficient in objective row is $$-5$$ for $$x_2$$.
- Identify leaving variable: ratio test $$\frac{8}{1} = 8$$ for slack variable $$s$$.
- Pivot on $$x_2$$ in row 1.
5. **Pivot operation:**
Make pivot element 1 (already 1), then eliminate $$x_2$$ from other rows.
New tableau:
\[
\begin{array}{c|ccc|c}
& x_1 & x_2 & s & RHS \\
\hline
x_2 & -2 & 1 & 1 & 8 \\
P & -2 & -5 & 0 & 0 \\
\end{array}
\]
Pivot row is row 1, so express $$x_2$$:
$$x_2 = 8 + 2x_1 - s$$
Substitute into objective row:
$$P = 2x_1 + 5x_2 = 2x_1 + 5(8 + 2x_1 - s) = 2x_1 + 40 + 10x_1 - 5s = 12x_1 + 40 - 5s$$
Rewrite objective row:
$$P - 12x_1 + 5s = 40$$
6. **Update tableau:**
\[
\begin{array}{c|ccc|c}
& x_1 & x_2 & s & RHS \\
\hline
x_2 & -2 & 1 & 1 & 8 \\
P & 12 & 0 & 5 & 40 \\
\end{array}
\]
7. **Check for optimality:**
All coefficients in objective row for non-basic variables are non-negative (12 for $$x_1$$ and 5 for $$s$$), so not optimal yet.
8. **Next pivot:**
Entering variable: $$x_1$$ (coefficient 12).
Ratio test for leaving variable:
From row 1: $$\frac{8}{-2}$$ is negative, so no positive ratio.
Since no positive ratio, the problem is unbounded in $$x_1$$ direction.
9. **Graphical method:**
Plot the constraint $$-2x_1 + x_2 \leq 8$$ and non-negativity constraints.
Rewrite constraint:
$$x_2 \leq 8 + 2x_1$$
The feasible region is below the line $$x_2 = 8 + 2x_1$$ in the first quadrant.
Since $$x_1, x_2 \geq 0$$, the feasible region is unbounded extending to the right and upwards.
10. **Objective function lines:**
Lines of constant $$P$$ are $$2x_1 + 5x_2 = c$$.
Increasing $$P$$ moves the line outward in the direction of vector $$(2,5)$$.
Because the feasible region is unbounded in the direction of increasing $$x_1$$ and $$x_2$$, and the objective function increases in that direction, the maximum is unbounded.
**Final conclusion:**
The linear program is unbounded; there is no finite maximum value for $$P$$.
Simplex Unbounded 61435C
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