Seki Takakazu

Hence, a target of Seki and his contemporary Japanese mathematicians was the development of general multi-variable algebraic equations and elimination theory. In his book of 1674, however, Seki only gave the single variable equations after the elimination, but no account of the process at all, nor his new system of algebraic symbols. In 1678, Tanaka Yoshizane (田中 由真), who was from Hashimoto’s school and was active in Kyoto, authored Sampo-meikai (算法明記), and gave new solutions to Sawaguchi’s 15 problems, using his version of multi-variable algebra, similar to Seki’s.

Source: en.wikipedia.org