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Use the technique developed in this section to solve the minimization problem. $$ \begin{aligned} \text { Minimize } & C=x-2 y+z \\ \text { subject to } & x-2 y+3 z \leq 10 \\ & 2 x+y-2 z \leq 15 \\ & 2 x+y+3 z \leq 20 \\ & x \geq 0, y \geq 0, z & \geq 0 \end{aligned} $$

Short Answer

Expert verified
To solve the given minimization problem, first, graph the constraint inequalities in three-dimensional space, and determine the feasible region as an intersection of these constraints. Next, find the vertices of the feasible region by solving the constraint equations. Then, evaluate the objective function \(C = x - 2y + z\) at each vertex, and choose the vertex with the minimum value of C as the optimal solution.

Step by step solution

01

Graph the constraint inequalities in three-dimensional space.

In order to graph the constraint inequalities, we first need to understand what they represent. Each inequality represents a plane in three-dimensional space. Since we have three inequalities, we are looking for the intersection of these three planes along with the non-negativity constraints \(x, y, z \geq 0\).
02

Determine the feasible region.

The feasible region is the intersection of all the constraint inequalities. In other words, we need to find the region of three-dimensional space that satisfies all the constraints simultaneously. This region represents all the possible solutions of the problem.
03

Find the vertices of the feasible region.

The vertices of the feasible region are the corner points where the constraint boundaries intersect. To find these vertices, we will solve the equations obtained by setting each constraint as an equality. In other words, we want to find points (x, y, z) that satisfy the following systems: 1. \(x - 2y + 3z = 10\) 2. \(2x + y - 2z = 15\) 3. \(2x + y + 3z = 20\) Additionally, we should consider the non-negativity constraints \(x, y, z \geq 0\).
04

Evaluate the objective function at each vertex.

Now that we have the vertices, we need to evaluate the objective function \(C = x - 2y + z\) at each vertex. This will give us the value of C at each corner point of the feasible region.
05

Choose the minimum value of C.

Finally, we just need to select the vertex which gives the minimum value of the objective function C. This vertex represents the optimal solution to the minimization problem.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Minimization Problem
When we talk about a minimization problem in linear programming, it refers to a type of optimization exercise where we aim to find the lowest possible value of an objective function, given a set of constraints.

In the case of our exercise, the objective function is given by the equation \( C = x - 2y + z \), and the goal is to minimize the value of \( C \) while adhering to certain restrictions. These restrictions, also called constraint inequalities, limit the values that \( x \), \( y \), and \( z \) can take, thereby influencing the outcome of the minimization process.

Linear programming problems, both minimization and maximization, are fundamental in various fields such as economics, logistics, and operations research, as they help in making the most efficient decisions with given resources.
Feasible Region
The feasible region is a key concept in linear programming, representing the set of all possible solutions that satisfy the constraints of the problem. In the case of our exercise, the feasible region is a three-dimensional space where all points adhere to the systems of inequalities provided.

It's important to visualize the feasible region as the volume or area, depending on the dimensionality of the problem, where all conditions are met. Only within this region can we find solutions that are 'feasible' or permissible. Sometimes the feasible region can be bounded or unbounded, and its shape and size can vastly impact the resolution of the problem.
Constraint Inequalities
Constraint inequalities are equations that limit the values that the variables in a linear programming problem can take. These inequalities define the edges and boundaries of the feasible region.

In our problem, we have three inequalities each representing a boundary in the space where the problem exists. The process of graphing these inequalities is vital as it assists us in visualizing the feasible region where these boundaries intersect.

Understanding of Constraint Inequalities

  • They provide a way to notate the limits of the problem’s variables.
  • Each inequality contributes to the shaping of the feasible region.
  • They must be simultaneously satisfied for a point to be within the feasible region.
Focusing on these inequalities helps us to systematically determine where our solution lies.
Non-negativity Constraints
Non-negativity constraints are a special subset of constraint inequalities that require all variables to be zero or positive. This is a common requirement in linear programming problems because in many real-world scenarios, negative solutions are not meaningful.

For example, in our exercise, the non-negativity constraints \( x \geq 0 \), \( y \geq 0 \), and \( z \geq 0 \) prevent us from considering any solution where the variables would represent negative quantities, like a negative amount of resources or a negative distance. These constraints are equally important as they influence the shape and position of the feasible region.
Objective Function
The objective function in a linear programming problem is the equation we aim to optimize; to either minimize or maximize.

For the minimization problem at hand, our objective function is \( C = x - 2y + z \). To solve the problem, we must evaluate this function at various points within the feasible region—specifically, at the vertices where the constraint boundaries intersect. By comparing the values of \( C \) at these points, we can identify the minimum value of the objective function, which gives us the optimized solution to the problem.

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Most popular questions from this chapter

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