Préfecture (capital): Périgueux[?].
Sous-préfectures: Bergerac[?], Nontron[?], Sarlat la Canéda[?].
See also: List of the communes of the Dordogne département
... this means that the parabola described by the quadratic equation touches the x-axis in a single point.) If the discriminant is positive, then there are two different ...