Re: Sum

*To*: mathgroup at smc.vnet.net*Subject*: [mg55221] Re: [mg55175] Sum*From*: "David Park" <djmp at earthlink.net>*Date*: Thu, 17 Mar 2005 03:28:41 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Why not use... x = Exp[-k]; Sum[x // Evaluate, {k, 0, Infinity}] E/(-1 + E) or even better f[k_] := Exp[-k] Sum[f[k], {k, 0, Infinity}] E/(-1 + E) ?? David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: mjumbo [mailto:mjumbo at nm.ru] To: mathgroup at smc.vnet.net Can sombody explain me why Sum[Exp[- k], {k, 0, Infinity}] gives the correct result, while the following (imho equivalent) statements 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. __________