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Ch. 5 - Systems of Equations and Inequalities
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 6, Problem 7

An objective function and a system of linear inequalities representing constraints are given. a. Graph the system of inequalities representing the constraints. b. Find the value of the objective function at each corner of the graphed region. c. Use the values in part (b) to determine the maximum value of the objective function and the values of x and y for which the maximum occurs.
A

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1
Step 1: Identify the objective function and the system of inequalities. The objective function is given by \(z = x + 8y\). The constraints are: \(x \geq 0\), \(y \geq 0\), \(6x + 5y \geq 30\), and \(4x + 5y \leq 40\).
Step 2: Graph the inequalities on the coordinate plane. Start by graphing the boundary lines for each inequality: \(x = 0\), \(y = 0\), \(6x + 5y = 30\), and \(4x + 5y = 40\). Use these lines to determine the feasible region that satisfies all inequalities simultaneously.
Step 3: Find the corner points (vertices) of the feasible region by solving the systems of equations formed by the intersection of the boundary lines. For example, find the intersection of \(6x + 5y = 30\) and \(4x + 5y = 40\), as well as intersections with the axes where \(x=0\) or \(y=0\).
Step 4: Evaluate the objective function \(z = x + 8y\) at each corner point found in Step 3. Substitute the \(x\) and \(y\) values of each vertex into the objective function to find the corresponding \(z\) values.
Step 5: Compare the values of \(z\) obtained at each corner point to determine the maximum value. Identify the corner point \((x, y)\) where this maximum occurs, which will be the solution to the optimization problem.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Graphing Systems of Linear Inequalities

Graphing systems of linear inequalities involves plotting each inequality on the coordinate plane and shading the region that satisfies the inequality. The solution to the system is the intersection of all shaded regions, representing all points that satisfy every constraint simultaneously.
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Feasible Region and Corner Points

The feasible region is the bounded area where all constraints overlap, representing all possible solutions. Corner points (vertices) of this region are critical because, in linear programming, the maximum or minimum value of the objective function occurs at one of these vertices.
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Evaluating the Objective Function at Corner Points

To find the maximum or minimum value of the objective function, substitute the coordinates of each corner point into the function. Comparing these values identifies which point yields the optimal solution, providing the maximum or minimum value and the corresponding values of variables x and y.
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