## Objective Variables

Objective variables are defined to construct an objective function. The objective function is a summation of all variables that are designated as objective-type. Variables are defined as objective function contributions by starting with **obj**. Thus, the variables *obj1*, *objective*, *object[1]* would be included in the objective function summation.

Additionally, slack variables are included in the objective function. These variables begin with the key letters **slk** and are defined with a lower bound of zero.

### Minimize vs. Maximize

The objective function is always minimized with APMonitor. Objective function maximization is accomplished by defining a new variable that is the negative of the minimized objective.

### Example

! Example model with an objective function Model example Parameters p1 = 5 End Parameters Variables objective v1 > 6 End Variables Equations objective = (v1 - p1)^2 End Equations End Model |

Solution p1 = 5 v1 = 6 objective = 1 |