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Homework Help: Cauchy's inequality?

  1. Mar 17, 2007 #1
    In the solutions sheet, they had this equation in the attachment as Cauchy's inequality. How can that be? Cauchy's inequality involves a multiplication instead of an addition on the right hand side.
     

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  2. jcsd
  3. Mar 17, 2007 #2

    Gib Z

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    Homework Helper

    We can't see the equation yet, but check what way the inequality sign is pointing..it doesn't always have to be the same side.
     
  4. Mar 17, 2007 #3
    I worked it out. What they did was add two bits (to the original inequality) to each side and factorised to get three instead of two parts in the inequality. If you square both sides than you get the original inequality back.
     
  5. Mar 17, 2007 #4

    HallsofIvy

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    Or work the other way: multiply out each term on the left hand side an use Cauchy's inequality on part of it.
     
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