Solve the following linear programming problem.

[tex]\[
\begin{array}{ll}
\text{Maximize:} & z = 6x + 2y \\
\text{Subject to:} & 6x - y \leq 15 \\
& 2x + y \geq 10 \\
& x \geq 2 \\
& y \leq 9
\end{array}
\][/tex]

The maximum value is [tex]$\square$[/tex] (Type an integer or a simplified fraction.)



Answer :

To solve the given linear programming problem, follow these step-by-step instructions:

### Step 1: Convert the Problem to Standard Form

The original problem is:
[tex]\[ \begin{array}{ll} \text{Maximize:} & z = 6x + 2y \\ \text{subject to:} & 6x - y \leq 15 \\ & 2x + y \geq 10 \\ & x \geq 2 \\ & y \leq 9 \end{array} \][/tex]

First, convert all constraints to the form [tex]\(Ax \leq b\)[/tex].

The second constraint [tex]\(2x + y \geq 10\)[/tex] can be rewritten as:
[tex]\[ -2x - y \leq -10 \][/tex]

Thus, our inequalities become:
[tex]\[ \begin{array}{ll} 6x - y \leq 15 \\ -2x - y \leq -10 \\ x \geq 2 \\ y \leq 9 \end{array} \][/tex]

### Step 2: Identify Variable Bounds

From the inequalities:
- [tex]\( x \geq 2 \)[/tex] implies a lower bound for [tex]\( x \)[/tex] of 2.
- [tex]\( y \leq 9 \)[/tex] implies an upper bound for [tex]\( y \)[/tex] of 9.

### Step 3: Solve the System of Linear Inequalities

Use linear programming techniques to find the optimal values of [tex]\( x \)[/tex] and [tex]\( y \)[/tex].

First, consider the intersection of the constraints by graphing or mathematical methods.
To find the feasible region, solve the system of equations formed by the intersecting constraints:

1. Solve [tex]\( 6x - y = 15 \)[/tex] and [tex]\( -2x - y = -10 \)[/tex]:

[tex]\[ \begin{align*} 6x - y &= 15 \quad \text{(i)} \\ -2x - y &= -10 \quad \text{(ii)} \end{align*} \][/tex]

Add equation (i) and (ii):

[tex]\[ 6x - y - 2x - y = 15 - 10 \][/tex]
[tex]\[ 4x - 2y = 5 \][/tex]
[tex]\[ 4x = 20 \Rightarrow x = 4 \][/tex]

Plug [tex]\( x = 4 \)[/tex] back into one of the original equations:

[tex]\[ 6(4) - y = 15 \][/tex]
[tex]\[ 24 - y = 15 \][/tex]
[tex]\[ y = 9 \][/tex]

The intersection point is [tex]\( (4, 9) \)[/tex].

### Step 4: Evaluate the Objective Function at Feasible Corners

Considering all constraints and variable bounds, the key feasible points you need to evaluate are located at:
- [tex]\( (2, 9) \)[/tex] (from [tex]\( x \geq 2 \)[/tex] and [tex]\( y \leq 9 \)[/tex])
- [tex]\( (4, 9) \)[/tex] (from the intersection above)

Evaluate [tex]\( z = 6x + 2y \)[/tex] at these points:

- For [tex]\( (2, 9) \)[/tex]:
[tex]\[ z = 6(2) + 2(9) = 12 + 18 = 30 \][/tex]

- For [tex]\( (4, 9) \)[/tex]:
[tex]\[ z = 6(4) + 2(9) = 24 + 18 = 42 \][/tex]

### Step 5: Determine the Maximum Value

The maximum value of [tex]\( z \)[/tex] among the feasible points is [tex]\( 42 \)[/tex], achieved at [tex]\( (4, 9) \)[/tex].

Hence, the maximum value is:
[tex]\[ \boxed{42} \][/tex]

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