Re: how to express one expression in terms of other expressions symbolically?

• To: mathgroup at smc.vnet.net
• Subject: [mg45764] Re: how to express one expression in terms of other expressions symbolically?
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Sat, 24 Jan 2004 03:28:11 -0500 (EST)
• Organization: Universitaet Leipzig
• References: <buqmak\$ra1\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

Eliminate[
{x^2 - z^2 == s,
(* equations for the substitution *)
q == x - z, r == x + z}, {x, z}]

as equations and elimimate the unwanted variables.

Regards
Jens

walala wrote:
>
> Dear all,
>
> I want to ask how to express the following terms into the form of (x1+x8),
> (x1-x8), (x2+x7), (x2-x7), etc. This is variable substitution. How can do
> this manipulation in mathematica symbolically?
>
> [ a01*x1+a02*x2+a03*x3+a04*x4+a04*x5+a03*x6+a02*x7+a01*x8]
> [ a05*x1+a06*x2+a07*x3+a08*x4-a08*x5-a07*x6-a06*x7-a05*x8]
> [ a09*x1+a10*x2-a11*x3-a12*x4-a12*x5-a11*x6+a10*x7+a09*x8]
> [ a13*x1-a14*x2-a15*x3-a16*x4+a16*x5+a15*x6+a14*x7-a13*x8]
> [ a17*x1-a18*x2-a19*x3+a20*x4+a20*x5-a19*x6-a18*x7+a17*x8]
> [ a21*x1-a22*x2+a23*x3+a24*x4-a24*x5-a23*x6+a22*x7-a21*x8]
> [ a25*x1-a26*x2+a27*x3-a28*x4-a28*x5+a27*x6-a26*x7+a25*x8]
> [ a29*x1-a30*x2+a31*x3-a32*x4+a32*x5-a31*x6+a30*x7-a29*x8]
>
> Thank you!
>
> -Walala

```

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