九章算術
The Greek mathematician Euclid (circa 300 BC) used geometric methods to solve quadratic equations in Book 2 of his "Elements", an influential mathematical treatise. Rules for quadratic equations appear in the Chinese "The Nine Chapters on the Mathematical Art" circa 200 BC. In his work "Arithmetica", the Greek mathematician Diophantus (circa 250 AD) solved quadratic equations with a method more recognizably algebraic than the geometric algebra of Euclid. His solution gives only one root, even when both roots are positive.