Why does multiplying two negative numbers equal a positive number?

Question

Why does multiplying two negative numbers equal a positive number?

In: 1210

Answer 1

It doesn’t have to be. There’s a book by Alberto A. Martínez called “Negative Math: How Mathematical Rules Can Be Positively Bent” that shows you can build a consistent mathematical system where a minus times a minus equals a minus:

https://press.princeton.edu/books/paperback/9780691133911/negative-math