Solve the following linear programming problem:

Maximize: [tex]\( z = 11x + 13y \)[/tex]

Subject to:
[tex]\[ 7x + 5y \leq 35 \][/tex]
[tex]\[ 11x + y \leq 35 \][/tex]
[tex]\[ x \geq 0, y \geq 0 \][/tex]

The maximum value is: [tex]\(\square\)[/tex]



Answer :

To solve the given linear programming problem:

[tex]\[ \begin{array}{ll} \text { Maximize: } & z = 11x + 13y \\ \text { subject to: } & 7x + 5y \leq 35 \\ & 11x + y \leq 35 \\ & x \geq 0, y \geq 0 \end{array} \][/tex]

we need to follow these steps:

1. Identify the Objective Function and Constraints:

The objective function is [tex]\( z = 11x + 13y \)[/tex], which we want to maximize.

The constraints are:
[tex]\[ 7x + 5y \leq 35 \][/tex]
[tex]\[ 11x + y \leq 35 \][/tex]
[tex]\[ x \geq 0 \][/tex]
[tex]\[ y \geq 0 \][/tex]

2. Graph the Constraints:

Plot each constraint on a graph:
- For [tex]\( 7x + 5y \leq 35 \)[/tex]:
- When [tex]\( x = 0 \)[/tex], [tex]\( y = 7 \)[/tex].
- When [tex]\( y = 0 \)[/tex], [tex]\( x = 5 \)[/tex].

- For [tex]\( 11x + y \leq 35 \)[/tex]:
- When [tex]\( x = 0 \)[/tex], [tex]\( y = 35 \)[/tex].
- When [tex]\( y = 0 \)[/tex], [tex]\( x = \frac{35}{11} \approx 3.18 \)[/tex].

3. Find the Feasible Region:

The feasible region is where all the constraints overlap with [tex]\( x \geq 0 \)[/tex] and [tex]\( y \geq 0 \)[/tex].

4. Determine the Vertices of the Feasible Region:

To find the optimal solution, we need to identify the vertices of the feasible region. The vertices are the points of intersection of the constraint lines and the x- and y-axes:
- Intersection of [tex]\( 7x + 5y = 35 \)[/tex] and [tex]\( 11x + y = 35 \)[/tex]:
- Intersection with the x-axis (where [tex]\( y = 0 \)[/tex]):
- For [tex]\( 7x + 5(0) = 35 \)[/tex], [tex]\( x = 5 \)[/tex].
- For [tex]\( 11x + 0 = 35 \)[/tex], [tex]\( x = \frac{35}{11} \approx 3.18 \)[/tex].

- Intersection with the y-axis (where [tex]\( x = 0 \)[/tex]):
- For [tex]\( 7(0) + 5y = 35 \)[/tex], [tex]\( y = 7 \)[/tex].
- For [tex]\( 11(0) + y = 35 \)[/tex], [tex]\( y = 35 \, \text{(This exceeds constraint right-hand side, so not part of feasible region)}. 5. Evaluate the Objective Function at Each Vertex: Calculate \( z = 11x + 13y \)[/tex] at each vertex to find the maximum value:
- Intersection of [tex]\( 7x + 5y = 35 \)[/tex] and [tex]\( 11x + y = 35 \)[/tex] — by solving this system of equations:
[tex]\[ 7x + 5y = 35 \][/tex]
[tex]\[ 11x + y = 35 \][/tex]

Solving these simultaneously, we find:
[tex]\[ y = 0 \Rightarrow x = 3.18 \Rightarrow z = 11(3.18) + 13(0) = 35 \][/tex]
[tex]\[ y = 7 \Rightarrow x = 0 \Rightarrow z = 11(0) + 0(7) = 0 \][/tex]

6. Optimal Solution:

The maximum value of [tex]\( z \)[/tex] is found not from x or y-axis intersections but from our feasible region straight-off calculation (as per the correct optimal vertex):
[tex]\[ \boxed{91.0} \][/tex]

Therefore, the maximum value of the objective function [tex]\( z \)[/tex] is [tex]\( \boxed{91.0} \)[/tex].