Around the year 820, in a round city called Baghdad, a young mathematician from Khwarizm (in modern Uzbekistan) sat down to write a book. He wanted to explain, in plain Arabic, how to solve problems where something was unknown.
He called the book al-Kitāb al-Mukhtaṣar fī Ḥisāb al-Jabr wa-l-Muqābala — "the Compendious Book on Calculation by Completion and Balancing". That phrase al-Jabr eventually became the English word algebra.
What did he actually do?
Al-Khwarizmi's breakthrough was that he gave us a method. Before him, maths problems were solved one at a time, like riddles. He showed that you could rearrange an equation — move things from one side to the other, cancel them out — and that every linear or quadratic equation could be solved the same way.
Every time a child moves an "x" across an equals sign, they're using his recipe.
The word that keeps travelling
Al-Khwarizmi's Latinised name was Algoritmi. That's where the English word algorithm comes from. Every time someone says "the YouTube algorithm", they're echoing a Muslim scientist from 1200 years ago.
Try this at home
Give your child this problem: "I'm thinking of a number. If I add 3 and then double the result, I get 14. What's the number?" Watch them discover al-Jabr on their own.