A negative number multiplied by another negative number results in a positive number. Most of us learnt this rule during our primary or secondary school years. 'Negative times negative equals positive' was a phrase that was drummed into us during mathematics lessons. In this article, we will prove it not just for numbers, but for any algebraic structure that, in a general sense, behaves somewhat like numbers. We will find out what that means shortly. First, let us see an illustration of this ...
