1. **State the problem:**
We want to maximize the objective function $$P = 35x_1 + x_2$$ subject to the constraints:
$$2x_1 + x_2 \leq 8$$
$$x_1 + 5x_2 \leq 8$$
with $$x_1, x_2 \geq 0$$.
2. **Introduce slack variables:**
To convert inequalities into equalities, add slack variables $$s_1$$ and $$s_2$$ for the first and second constraints respectively:
$$2x_1 + x_2 + s_1 = 8$$
$$x_1 + 5x_2 + s_2 = 8$$
where $$s_1, s_2 \geq 0$$.
3. **Rewrite the objective function for the simplex method:**
We write the objective function as:
$$P - 35x_1 - x_2 = 0$$
4. **Initial system with slack variables:**
\[
\begin{cases}
2x_1 + x_2 + s_1 = 8 \\
x_1 + 5x_2 + s_2 = 8 \\
P - 35x_1 - x_2 = 0
\end{cases}
\]
5. **Simplex tableau:**
Set up the tableau with variables $$x_1, x_2, s_1, s_2, P$$:
$$
\begin{array}{c|cccc|c}
& x_1 & x_2 & s_1 & s_2 & RHS \\
\hline
s_1 & 2 & 1 & 1 & 0 & 8 \\
s_2 & 1 & 5 & 0 & 1 & 8 \\
-P & -35 & -1 & 0 & 0 & 0
\end{array}
$$
6. **Identify entering and exiting variables:**
- Entering variable: The variable with the most negative coefficient in the bottom row is $$x_1$$ (coefficient $$-35$$).
- Compute ratios for pivot row:
- For $$s_1$$: $$\frac{8}{2} = 4$$
- For $$s_2$$: $$\frac{8}{1} = 8$$
- Exiting variable: The smallest positive ratio is 4, so $$s_1$$ leaves the basis.
- Pivot element is 2 in row 1, column $$x_1$$.
7. **Perform pivot operation:**
Divide row 1 by pivot element 2:
$$
\begin{array}{c|cccc|c}
& x_1 & x_2 & s_1 & s_2 & RHS \\
\hline
s_1 & \cancel{2}/2 & \frac{1}{2} & \frac{1}{2} & 0 & 4 \\
s_2 & 1 & 5 & 0 & 1 & 8 \\
-P & -35 & -1 & 0 & 0 & 0
\end{array}
\Rightarrow
\begin{array}{c|cccc|c}
& x_1 & x_2 & s_1 & s_2 & RHS \\
\hline
x_1 & 1 & \frac{1}{2} & \frac{1}{2} & 0 & 4 \\
s_2 & 1 & 5 & 0 & 1 & 8 \\
-P & -35 & -1 & 0 & 0 & 0
\end{array}
$$
Subtract row 1 from row 2:
$$
\begin{aligned}
s_2 & : (1 - 1)x_1 + (5 - \frac{1}{2})x_2 + (0 - \frac{1}{2})s_1 + (1 - 0)s_2 = 8 - 4 \\
& = 0x_1 + \frac{9}{2}x_2 - \frac{1}{2}s_1 + s_2 = 4
\end{aligned}
$$
Update row 2:
$$
\begin{array}{c|cccc|c}
& x_1 & x_2 & s_1 & s_2 & RHS \\
\hline
x_1 & 1 & \frac{1}{2} & \frac{1}{2} & 0 & 4 \\
s_2 & 0 & \frac{9}{2} & -\frac{1}{2} & 1 & 4 \\
-P & -35 & -1 & 0 & 0 & 0
\end{array}
$$
Add 35 times row 1 to row 3:
$$
\begin{aligned}
-P & : (-35 + 35 \times 1)x_1 + (-1 + 35 \times \frac{1}{2})x_2 + (0 + 35 \times \frac{1}{2})s_1 + 0s_2 = 0 + 35 \times 4 \\
& = 0x_1 + ( -1 + 17.5 )x_2 + 17.5 s_1 + 0 = 140
\end{aligned}
$$
Update row 3:
$$
\begin{array}{c|cccc|c}
& x_1 & x_2 & s_1 & s_2 & RHS \\
\hline
x_1 & 1 & \frac{1}{2} & \frac{1}{2} & 0 & 4 \\
s_2 & 0 & \frac{9}{2} & -\frac{1}{2} & 1 & 4 \\
-P & 0 & 16.5 & 17.5 & 0 & 140
\end{array}
$$
8. **Check for optimality:**
All coefficients in the bottom row for variables $$x_1$$ and $$x_2$$ are now non-negative, so the current solution is optimal.
9. **Solution:**
From the tableau:
$$x_1 = 4, \quad x_2 = 0, \quad s_1 = 0, \quad s_2 = 4$$
Maximum value of $$P$$ is:
$$P = 35(4) + 0 = 140$$
**Final answer:** $$x_1 = 4, x_2 = 0, P_{max} = 140$$
Simplex Method 3343Ab
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