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MathGroup Archive 2000

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wrong Factor[] result

  • To: mathgroup at smc.vnet.net
  • Subject: [mg25649] wrong Factor[] result
  • From: Gianluca Gorni <gorni at dimi.uniud.it>
  • Date: Wed, 18 Oct 2000 02:52:23 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hello!

Take the polynomial

  pol = a^2 + 2b^2;

and factorize it this way:

  res = Factor[pol, Extension -> {Sqrt[-2]/3}]

  Out -> ((-3*I*a + Sqrt[2]*b)*(3*I*a + Sqrt[2]*b))/9

This result is wrong! Just expand it:

  Expand[res]

  Out ->  a^2 + (2b^2)/9

I get a correct result if I factor for example as

Factor[pol, Extension -> {Sqrt[-2]}]

My version is 4.0 for PowerMac.

         Gianluca Gorni


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