Non-negativity constraint
A non-negativity constraint prevents a decision variable from taking values below zero where negative production, sales or resource use has no meaningful interpretation. In a linear programme it is usually written x ≥ 0, y ≥ 0 and similarly for other variables. It defines part of the feasible region but does not require variables to be whole numbers. Integer requirements are a separate modelling restriction.
Worked example
If x is units of product A made, x ≥ 0 excludes a mathematically convenient negative quantity from the solution.
Common mistake
Non-negative permits zero and fractional values. Do not assume it automatically enforces whole-unit production.
Where it appears in your exams
| Qualification | Exam | Relationship | Period |
|---|---|---|---|
| ACCA | PM | Direct | September 2026–June 2027 |