Dummy Variables

If the constraints of given LP problem are greater than or equal to type, in that case the constraints are converted into equations by subtracting surplus variables. In such a case, an identity matrix does not form with the coefficients of surplus variables. In order to obtain an identity matrix, the auxiliary non-negative variables are added to given constraints. Such additional variables are called artificial variables (dummy variables). These are denoted by D1, D2 or A1, A2 etc. When the given constraints are greater than or equal to and equal to type, the dummy variables are added.

If the objective function is to maximize a certain quantity, the coefficient of each dummy variable in objective function is assumed to be a very high positive number which is denoted by M.