Jia Xian

According to the history of the Song dynasty, Jia was a palace eunuch of the Left Duty Group.

He studied under the mathematician Chu Yan, and was well versed in mathematics, writing many books on the subject.

Jia used it as a tool for extracting square and cubic roots.

The original book by Jia entitled Shi Suo Suan Shu was lost; however, Jia's method was expounded in detail by Yang Hui, who explicitly acknowledged his source: "My method of finding square and cubic roots was based on the Jia Xian method in Shi Suo Suan Shu.

Jia Xian's additive-multiplicative method implemented the "Horner" rule.