       Re: Solve[] doesn't

• To: mathgroup at smc.vnet.net
• Subject: [mg90626] Re: [mg90619] Solve[] doesn't
• From: Curtis Osterhoudt <cfo at lanl.gov>
• Date: Thu, 17 Jul 2008 05:32:34 -0400 (EDT)
• Organization: LANL
• References: <200807161029.GAA08789@smc.vnet.net>

```  Is your syntax correct? Especially your equal signs are assignments, rather
than tests for equality. When those are changed, at least in v. 6.0.3 for
linux, things work fine:

eqns = {x - y == 1, x^2 + y^2 == 3, x^3 - y^3 == 4}

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

OR

Eliminate[eqns, y]
-x + x^2 == 1

Solve[%, x]
{{x -> (1/2)*(1 - Sqrt)}, {x -> (1/2)*(1 + Sqrt)}}

On Wednesday 16 July 2008 04:29:42 Hauke Reddmann 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?

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```

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