It’s something we all know, right?
Negative times a negative equals positive.
Of course, we know that!
Except when someone innocently asks us why.
And continues asking, if negative times a negative is positive, why is positive times a positive not negative?
What kind of a question is that?! EVERYONE knows negative times negative equals positive, negative times positive equals negative, positive times negative equals negative and negative times negative equals positive. Turns out not many people know the reason. It’s just something we have been told and we learn it by rote and that’s it.
It’s inspired by Gowri. He asked this question to me and stumped me, because even after having a Master’s degree in Maths from IIT B, I didn’t quite know the answer. I had to think and do a bit of reading before my solution was born 🙂
There are many ways to show all of the above, but here is my super simple and fairly elegant explanation.
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