The 14 "eight-thousanders[?]", 8,000 m or higher, all in the Himalayas:
By continent:
Europe
Asia
North America
South America
Africa
Oceania
Antarctica
Mars
See also: Mountain range, List of mountain ranges, List of volcanoes
... of the quadratic equation, because it discriminates between three qualitatively different cases: If the discriminant is zero, then there is a repeated solution x, and ...