(October 12, 2013 at 3:45 pm)Tiberius Wrote:(October 12, 2013 at 10:33 am)Chas Wrote: Seriously? You want me to re-derive the already proven Associative and Distributive Laws of arithmetic?No, not at all. The point was, you had to use those laws to show that two negative numbers, when multiplied, become a positive number.
Your demonstration didn't do that. All you did was multiply both sides by -1...twice. The second one of the those multiplications had you multiplying -1 with -20, and producing 20, without showing why that was the case.
Quote:The demonstration was to show there is no mystery or confusion about the OP's question.Ok, but it doesn't answer OP's question, which was why -4 * -5 = 20.
All your answer did was move the focus point of the question, so now it's: why does -1 * -20 = 20?
You can't prove things in mathematics with a single example.
The OP didn't express a problem with anything but the multiplication of two negative numbers resulting in a positive number.
Your comments have nothing to do with either his question or my answer.
Skepticism is not a position; it is an approach to claims.
Science is not a subject, but a method.
Science is not a subject, but a method.
