RE: Summation without Mathematica
- To: mathgroup at smc.vnet.net
- Subject: [mg27449] RE: [mg27416] Summation without Mathematica
- From: "David Park" <djmp at earthlink.net>
- Date: Sun, 25 Feb 2001 20:55:55 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Sum[x^3*a^x, {x, 1, Infinity}]
% /. a -> 7/8
(a + 4*a^2 + a^3)/(-1 + a)^4
18872
David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/
> From: mrtommorris [mailto:mor3752 at alltel.net]
To: mathgroup at smc.vnet.net
>
> Can someone help me to evaluate the sum from x=1 to infinity for the
> expression x^3(7/8)^x. I know the formulas that will evaluate
> either alone.
> But the product is giving me difficulty.
>