Why a Negative x Negative = Positive
Date: 4/11/96 at 16:57:21 From: Anonymous Subject: proofs, multiplying integers A teacher in a course I took last fall challenged us to come up with a way to demonstrate or prove how it is that a negative times a negative equals a positive (how to explain this). The only thing I could come up with is that it is positive because one is negating a negative. No one came up with a very satisfying explanation. Can you help? Thanks.
Date: 4/18/96 at 13:26:36 From: Anonymous Subject: Math equations Hello. I am a student at The Colorado Institute of Art and have had a question/problem presented to me by our Gen ED math instructor. The question is: Are there any other forms of proof to show that (- + - = +) Negative plus a negative equals a positive? I have done more researching than one brain could handle, and I was hoping that with several brains together the answer could be completed. I would greatly appreciate your help in any way. Thank you very much. Julia
Date: 5/3/96 at 14:42:2 From: Doctor Steven Subject: Re: proofs, multiplying integers Well, when we say -1 we mean the additive inverse of 1 so we have: 1 + -1 = 0 (since they are inverses) 1 + (1)*-1 = 0 (1 multiplied by anything is that thing) 1 = -(1)*-1 (subtract (1)*-1 from both sides) 1 = -1*-1 (the parenthesis don't mean anything) So a negative times a negative means a positive. Hope this helps. -Doctor Steven, The Math Forum
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