Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2008

[Date Index] [Thread Index] [Author Index]

Search the Archive

Cannot Factor an expression

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87563] Cannot Factor an expression
  • From: Francogrex <franco at grex.org>
  • Date: Sun, 13 Apr 2008 03:31:17 -0400 (EDT)

If Factor is effectively the reverse of expand, then how come factor
cannot find back the expression below?

Expand[Sum[(Subscript[z, i] - 1)*(\[Mu] - Subscript[x, i])^2, {i, 1,
3}]]

Factor[-3*\[Mu]^2 + 2*\[Mu]*Subscript[x, 1] - Subscript[x, 1]^2 +
   2*\[Mu]*Subscript[x, 2] - Subscript[x, 2]^2 + 2*\[Mu]*Subscript[x,
3] -
   Subscript[x, 3]^2 + \[Mu]^2*Subscript[z, 1] -
   2*\[Mu]*Subscript[x, 1]*Subscript[z, 1] + Subscript[x, 1]^2*
    Subscript[z, 1] + \[Mu]^2*Subscript[z, 2] -
   2*\[Mu]*Subscript[x, 2]*Subscript[z, 2] + Subscript[x, 2]^2*
    Subscript[z, 2] + \[Mu]^2*Subscript[z, 3] -
   2*\[Mu]*Subscript[x, 3]*Subscript[z, 3] + Subscript[x, 3]^2*
    Subscript[z, 3]]

Is there some additional arguments to the function factor so that it
can find back the original:
Sum[(Subscript[z, i] - 1)*(\[Mu] - Subscript[x, i])^2, {i, 1, 3}]

Thanks for help with this


  • Prev by Date: waiting for pressed key and reading key
  • Next by Date: Re: color scale for plot
  • Previous by thread: Re: waiting for pressed key and reading key
  • Next by thread: Re: Cannot Factor an expression