Al-Khwarizmi most important work Hisab al-jabr w'al-muqabala written in 830 gives us the word algebra . This treatise classifies the solution of quadratic equations and gives geometric methods for completing the square. No symbols are used and no negative or zero coefficients were allowed.
Al-Khwarizmi also wrote on Hindu-Arabic numerals. The Arabic text is lost, but a Latin translation, Algoritmi