# Slack variable

In an inequality constraint of the form $LaTeX: \textstyle g(x) \le b,$ the slack is $LaTeX: \textstyle b - g(x),$ which is designated by the slack variable, $LaTeX: s$. Then, the original constraint is equivalent to the defining equation, $LaTeX: \textstyle g(x) + s = b, \mbox{ plus } s \ge 0.$