Simplex method barely giving the correct answer when using tableaus

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SUMMARY

The discussion centers on the application of the simplex method to solve a linear programming problem, specifically using a tableau format. The user attempts to maximize the objective function 4x1 + x2 + 3x3 under given constraints but encounters a discrepancy between the tableau's optimal objective value of 41/4 and the known correct answer of 10. The user correctly applies Bland's rule for pivot selection but seeks clarification on the inconsistency in the results derived from the tableau.

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Homework Statement



I am trying to solve the follwing linear program

<br /> \max \qquad 4x_1+x_2+3x_3<br />
<br /> \text{s.t }\qquad x_1+4x_2\qquad\,\leq1<br />
<br /> \quad\quad\quad\quad\quad\quad3x_1-x_2+x_3\leq3<br />

The Attempt at a Solution


Using the simplex method and a tableau (negated objective function in the last row, right-hand side of constraints in the last column):

<br /> \begin{matrix}<br /> \textcircled{1}&amp;4&amp;0&amp;1&amp;0&amp;1\\<br /> 3&amp;-1&amp;1&amp;0&amp;1&amp;3\\\hline<br /> -4&amp;-2&amp;-3&amp;0&amp;0&amp;0<br /> \end{matrix}<br /> \rightarrow<br /> \begin{matrix}<br /> 1&amp;4&amp;0&amp;1&amp;0&amp;1\\<br /> 0&amp;-13&amp;\textcircled{1}&amp;-3&amp;1&amp;0\\\hline<br /> 0&amp;14&amp;-3&amp;4&amp;0&amp;4<br /> \end{matrix}<br /> \rightarrow<br /> \begin{matrix}<br /> 1&amp;\textcircled{4}&amp;0&amp;1&amp;0&amp;1\\<br /> 0&amp;-13&amp;1&amp;-3&amp;1&amp;0\\\hline<br /> 0&amp;-25&amp;0&amp;-5&amp;3&amp;4<br /> \end{matrix}<br /> \rightarrow<br /> \begin{matrix}<br /> 1/4&amp;1&amp;0&amp;1/4&amp;0&amp;1/4\\<br /> 13/4&amp;0&amp;1&amp;1/4&amp;1&amp;13/4\\\hline<br /> 25/4&amp;0&amp;0&amp;5/4&amp;3&amp;41/4<br /> \end{matrix}<br />

From which I conclude that the optimal objective value is 41/4
and the optimal solution is (0,1/4,13/4).

Inserting the optimal solution in the objective function does NOT yield 41/4.
It yields 10. I know from the textbook that the correct answer is 10, so my solution is correct. Can anyone explain then why my objective value in the tableau is not?
 
Last edited:
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Please note that I have chosen my pivots by Bland's rule
 

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