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Sign Switching


Date: 01/28/2002 at 09:16:51
From: Marielle
Subject: Multiplying / dividing inequalities

Can you explain sign switching for me? I don't get why or when the 
sign switches.


Date: 01/28/2002 at 11:45:27
From: Doctor Ian
Subject: Re: Multiplying / dividing inequalities

Hi Marielle, 

I think this answer from the Dr. Math archives will tell you what you 
want to know, but write back if it isn't clear, or if you still have 
questions.

   Negatives and Inequalities
   http://mathforum.org/dr.math/problems/jain9.10.98.html   

For what it's worth, you might try thinking in terms of maintaining an 
advantage.  For example, if I have more of something than someone 
else, 

  my stuff > his stuff

then if each of us adds or subtracts the same amount of stuff, I'll 
still be better off; and if we each multiply what we have by some 
positive amount, I'll still be better off.  

But what happens if we both convert our assets into the same amount of 
debt?  (That is, for every dollar of assets I had, I now have a dollar 
of debt.) In that case, the better off I am to begin with, the worse 
off I am after the switch. 

Does this help? 

- Doctor Ian, The Math Forum
  http://mathforum.org/dr.math/   


    
Associated Topics:
High School Basic Algebra
Middle School Algebra

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