How do I find the Dual of the LP

min $ = 4y_1 +2y_2 - y_3 $

$s.t. y_1 + 2y_2 +2y_3 <= 6$

$s.t. y_1- y_2 + 2y_3 = 8$

$y_1, y_2 >= 0, y_3 $urs

How do I find the dual to this LP? What confuses me is the = sign. Also the urs variable. I'm not sure how to act on these.


Solution 1:

With the table below you do not need to transform $y_3$. You have to read the table from right to left, since the primal problem is min-problem. The dual of the LP is

$\texttt{max} \ \ 6u_1+8u_2$

$u_1+u_2\leq 4 \quad (y_1)$

$2u_1-u_2\leq 2 \quad (y_2)$

$2u_1+2u_2=8 \quad (y_3)$

$u_1\leq 0, u_2 \text{ unrestr.}$

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