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Re: Sum

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

From: mjumbo [mailto:mjumbo at]
To: mathgroup at

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.

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