cartesiandaemon (cartesiandaemon) wrote,
cartesiandaemon
cartesiandaemon

Minus times minus

Can you remember when you first learnt/understood that a negative number times a negative number gave a positive number?

Did you think that makes sense? Did you think it should be negative, or were you just not sure?

I'm sure I'd learnt the rule before then, but I remember working out an explanation for why it makes sense (imagine you give out numbers of merits or demerits to people; taking back a number of demerits is the same as giving that number of merits). Before then, I didn't see why it should be positive, though I don't think I thought it should be be negative, I just didn't understand why.

Conversely, some people think the other way round. Negative Math: How Mathematical Rules Can Be Positively Bent. I haven't read all of his book, so I don't know if it's a good explanation of why and how mathematical rules are chosen, or if he's smoking bad weed. It could be either.

I do know it made me queasy. He seems to think minus times minus giving minus is more obvious, and perhaps should be standard, and that mathematics is a conspiracy against this.
Tags: maths, poll, witterings
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