The Chinese phrase Four Great Ancient Capitals of China (中国四大古都 pinyin zhong1 guo2 si4 da4 gu3 du1) refers to Nanjing, Beijing, Xi'an, and Luoyang.
... If the discriminant is positive, then there are two different solutions x, both of which are real. (Geometrically, this means that the parabola intersects the x-axis ...