This is the epigraph form of the problem. You try to find the point with the lowest height in the epigraph. https://en.wikipedia.org/wiki/Epigraph_(mathematics

This is the epigraph form of the problem. You try to find the point with the lowest height in the epigraph. https://en.wikipedia.org/wiki/Epigraph_(mathematics) https://en.wikipedia.org/wiki/Epigraph_(mathematics)