Consider a linear programming problem with two variables and two constraints. The objective function is : Maximize X₁ + X₂ . The corner points of the feasible region are (0, 0), (0, 2), (2, 0) and (4/3, 4/3). Let Y₁ and Y₂ be the decision variables of the dual and v₁ and v₂ be the slack variables of the dual of the given linear programming problem. The optimum dual variables are

$\text{We know,}\\ \text{The inequality constraints are changed to equality constraints by adding or subtracting a non-negative variable from the left-hand sides of such constraints.}\\ \text{These variable is called slack variables or simply slacks.}\\ \text{They are added if the constraints are $(\leq)$ and subtracted if the constraints are $(\geq).These variables can remain positive throughout the process of solution and their values in the optimal solution given useful information about the problem.$}$ Hence,Optimum dual variables are $v_1$ and $v_2$.