Multiplying the two inequalities

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    Inequalities
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Discussion Overview

The discussion revolves around the multiplication of two inequalities, specifically the inequalities x-y≤a-b≤x+y and t-g≤c-d≤t+g. Participants explore the conditions under which such multiplication is valid and the implications of the signs of the terms involved.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the method of multiplying inequalities and seeks clarification on the process.
  • Another participant suggests that if all terms are positive, term-by-term multiplication is acceptable, but warns against it if there is uncertainty about the signs of the terms.
  • A further reply emphasizes that without knowing whether the expressions can be negative, valid multiplication into new inequalities cannot be performed.
  • It is proposed that if all individual numbers are positive, the inequalities can be rearranged before multiplication.

Areas of Agreement / Disagreement

Participants express differing views on the conditions necessary for multiplying inequalities, indicating that the discussion remains unresolved regarding the validity of the multiplication under various conditions.

Contextual Notes

There are limitations regarding the assumptions about the signs of the terms involved, which affect the validity of the proposed multiplication of inequalities.

Quarlep
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Lets suppose we have two inequalities,
First inequality is x-y≤a-b≤x+y
Second inequality is t-g≤c-d≤t+g How can I multiply these inequalities

Thanks
 
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What do you have in mind by multiplying inequalities? In any case if all the terms are positive then term by term multiplication is OK. Otherwise be very careful.
 
Thanks
 
If you do not know whether these expressions can be negative, you can't validly multiply inequalities into new inequalities.

If you DO know that all the 8 individual numbers are, say, positive, you may first rearrange your inequalities, to for example:
x+b<=a+y<=x+2y+b and THEN multiply with the similary rearranged second inequality.
 

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