Interpretation of Slack Variables - Conclusions Previous Next
The Constraints with Slack Variables
Conclusions
The simplex method needs functional constraints to be expressed as equations. Therefore, slack variables are are used to convert functional constraints with a  sign into a functional constraint with an = sign. The new form of these constraints becomes equivalent to the original form by also adding nonegativity constraints for the slack variables.
As shown on the right above, the new form of the functional constraints provides a convenient system of equations for the simplex method. It is also convenient for the simplex method to include the equation for the objective function,
 , with this system of equations. After bringing the variables over to the left-hand side, this additional equation becomes 
The last page will incorporate this into the overall problem.