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.
... 2a is zero and it is impossible to divide by it.) The symbol <math>\pm \sqrt {b^2-4ac}</math> in the formula should be understood as "either of thos ...