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Re: Sum

  • To: mathgroup at
  • Subject: [mg55211] Re: Sum
  • From: bghiggins at
  • Date: Thu, 17 Mar 2005 03:28:29 -0500 (EST)
  • References: <d192qe$ng4$>
  • Sender: owner-wri-mathgroup at

Sum has the attribute HoldAll, so its arguments are held in an
unevaluated form. Simply wrap the first argument of Sum with Evalaute

Sum[Evaluate[x], {k, 0, Infinity}]


mjumbo wrote:
> Can sombody explain me why
> Sum[Exp[- k], {k, 0, Infinity}]
> gives the correct result, while the following (imho equivalent)
> x = Exp[-k]
> Sum[x, {k, 0, Infinity}]
> don't? What should I do to make it work? It is rather vexing to
copy/paste long expressions instead of using short placeholders like x.
> __________
> -- Íîâàÿ Ïî÷òà: âñå ïî-íîâîìó.

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