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Name: Mehdi
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Question:
How do you explain -1*-1=+1 (without using velocity, direction and time)



Replies:
Multiplication by -1 is reflection through the origin. A number becomes its counterpart on the other side of zero. Clearly, if you reflect a number twice through the origin (multiply twice by -1), then that is the same as doing nothing at all (multiplying once by 1).

Grayce


Hello,

My guess is that this is a concept, a convention, an assumption, or an agreement, based on which other relationships can be expressed and derived. I recommend looking into a reference book on the history of mathematics to learn about its invention and justifications.

AK

Dr. Ali Khounsary



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