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Re: Solve[] doesn't

  • To: mathgroup at smc.vnet.net
  • Subject: [mg90650] Re: [mg90619] Solve[] doesn't
  • From: DrMajorBob <drmajorbob at att.net>
  • Date: Thu, 17 Jul 2008 05:37:09 -0400 (EDT)
  • References: <27108604.1216206736191.JavaMail.root@m08>
  • Reply-to: drmajorbob at longhorns.com

If y is eliminated, there IS no solution for x:

Solve[{x - y == 1, x^2 + y^2 == 3, x^3 - y^3 == 4}, {x, y}]

{{x -> 1/2 (1 - Sqrt[5]),
   y -> 1/2 (-1 - Sqrt[5])}, {x -> 1/2 (1 + Sqrt[5]),
   y -> 1/2 (-1 + Sqrt[5])}}

As you can see, x and y depend on each other.

Bobby

On Wed, 16 Jul 2008 05:29:42 -0500, Hauke Reddmann  
<fc3a501 at uni-hamburg.de> wrote:

> This is extremely annoying.
> I have a very large (this seems to be critical) equation
> system. It's partly linear, partly horror, but already
> after I solve the linear part, a certain solution (which
> is obviously one since substituting it in makes all equations
> identical zero) can't be found anymore. The solution has some
> surds (this also seems critical, the ones without are found)
> but the equations are strictly polynomic.
>
> Faked Example (the real one only PM-ed, since it's a bit
> oversized):
>
> x-y=1
> x^2+y^2=3
> x^3-y^3=4
> and after y was eliminated, it doesn't find x. (=golden mean here)
>
> Huh?
> --
> Hauke Reddmann <:-EX8    fc3a501 at uni-hamburg.de
>     Er-a svo gott     sem gott kveða
>     öl alda sonum,     því að færra veit
>     er fleira drekkur     síns til geðs gumi.
>
>



-- 
DrMajorBob at longhorns.com


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