I am reading In the Land of Invented Languages by Arika Okrent. It's light and fun and educational. It's about made-up languages and what they tell us about how we look at language. It tells me that mathematical notation wasn't invented until a few hundred years ago. Here's how the Babylonians wrote the Pythagorean Theorem (a^2+b^2=c^2):

"4 is the length and 5 the diagonal. What is the breadth? Its size is not known. 4 times 4 is 16. 5 times 5 is 25. You take 16 from 25 and there remains 9. What times what shall I take in order to get 9? 3 times 3 is 9. 3 is the breadth."That's on page 30. Amazing, right? I'm dumbfounded!

I would like to learn more about the history of mathematical notation, if anyone has that info. Thanks.