Farkas lemma
= Farkas lemma
{c}
{title2=$Az=b,\ z\geq0\quad\text{or}\quad A^Ty\geq0,\ b^Ty<0$}
{wiki=Farkas'_lemma}
= Farkas alternative
{c}
{synonym}
Exactly one of the two displayed systems is feasible. <Closedness of finitely generated cones> and the <Fenchel-Moreau theorem> applied to a cone's <indicator functional> provide a proof through its polar cone. It yields a nonnegative multiplier certificate when a finite system of linear inequalities is inconsistent.