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Determine whether the statement is true or false. If it is true, explain why it is true. If it is false, give an example to show why it is false. Choosing the pivot row by requiring that the ratio associated with that row be the smallest ensures that the iteration will not take us from a feasible point to a nonfeasible point.

Short Answer

Expert verified
The statement is true. Choosing the pivot row by requiring the smallest ratio associated with that row ensures that the iteration will not take us from a feasible point to a nonfeasible point. This is because, by selecting the smallest ratio as our pivot row, we move along the entering variable's direction without exceeding the bounds of any constraint, thus maintaining feasibility.

Step by step solution

01

Understand the statement and the context

In the context of linear programming, the statement we need to analyze is related to the Simplex method, an algorithm for solving linear optimization problems with an iterative process for finding an optimal solution. The pivot row is used when transforming the system of linear equations to get an improved solution through Gaussian elimination (swapping out the leaving variable with the incoming variable). The pivot row is chosen using the rule mentioned in the statement, i.e. the smallest ratio associated with that row. Now, we will either provide evidence to prove the statement true or provide a counterexample if it's false.
02

Analyze the smallest ratio rule

The rule mentioned in the given statement is the smallest ratio rule which states that we should choose the pivot row by requiring the smallest ratio associated with that row. This rule is used to choose the leaving variable (one associated with the pivot row) and is intended to ensure that the feasibility of the solution is maintained at each iteration. The ratio is calculated by dividing the available resources (b) by the corresponding coefficient of the entering variable (a) in each constraint. The smallest positive ratio determines the leaving variable (pivot row): \[\text{Ratio} = \frac{b_i}{a_{ij}}\] where i represents the constraint row and j represents the entering variable column.
03

Determine the truth of the statement

The statement, "Choosing the pivot row by requiring that the ratio associated with that row be the smallest ensures that the iteration will not take us from a feasible point to a nonfeasible point", is actually true. Let's explain why that is the case.
04

Explain why the statement is true

In the context of linear programming, a feasible solution is one that satisfies all the constraints of the problem. When using the simplex method, it is essential to maintain feasibility as we move from one iteration to another. By selecting the pivot row using the smallest ratio rule, we ensure that we do not violate the constraints of the problem. The reason behind this is that the smallest ratio is associated with the tightest constraint. By selecting the smallest ratio as our pivot row, we move along the entering variable's direction without exceeding the bounds of any constraint, thus maintaining feasibility. By adhering to the smallest ratio rule, we can be sure that the constraint taking us to the boundary doesn't make any other constraint infeasible. So, the statement is true. Choosing the pivot row by requiring the smallest ratio associated with that row ensures that the iteration will not take us from a feasible point to a nonfeasible point.

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Most popular questions from this chapter

Rewrite each linear programming problem as a maximization problem with constraints involving inequalities of the form \(\leq\) a constant (with the exception of the inequalities \(x \geq 0, y \geq 0\), and \(z \geq 0\) ). $$ \begin{aligned} \text { Minimize } & C=5 x+10 y+z \\ \text { subject to } & 2 x+y+z \geq 4 \\ & x+2 y+2 z \geq 2 \\ & 2 x+4 y+3 z \leq 12 \\ x & \geq 0, y \geq 0, z \geq 0 \end{aligned} $$

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