Interregnum 1383-1385
House of Aviz[?] 1385-1580
Habsburg
House of Braganza[?] 1640-1807
House of Braganza, Restored 1814-1910
The chronology continues on Presidents of Portugal
See also: History of Portugal -- Lists of incumbents
... (Geometrically, this means that the parabola intersects the x-axis in two points.) If the discriminant is negative, then there are two different solutions x, both of ...