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MathGroup Archive 2006

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Re: message question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg70953] Re: [mg70918] message question
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 2 Nov 2006 06:48:56 -0500 (EST)
  • Reply-to: hanlonr at cox.net

expr=x^3+2*x^2-1;

sols=Solve[expr==0];

And@@Thread[Simplify[expr/.sols]==0]

True


Bob Hanlon

---- dimitris <dimmechan at yahoo.com> wrote: 
> Consider the following
> 
> sols = Solve[x^3 + 2*x^2 - 1 == 0]
> {{x -> -1}, {x -> (1/2)*(-1 - Sqrt[5])}, {x -> (1/2)*(-1 + Sqrt[5])}}
> 
> Why do they appear the warning messages in the following command?
> 
> x^3 + 2*x^2 - 1 == 0 /. sols
> N::meprec: Internal precision limit $MaxExtraPrecision =
> 49.99999999999999` \
> reached while evaluating \!\(\(-1\) + 1\/2\ \((\(-1\) - \@5)\)\^2 +
> 1\/8\ \(\(\((\(-1\) - \
> \@5)\)\^3\)\(.\)\)\)
> N::meprec: Internal precision limit $MaxExtraPrecision =
> 49.99999999999999` \
> reached while evaluating \!\(\(-1\) + 1\/2\ \((\(-1\) - \@5)\)\^2 +
> 1\/8\ \(\(\((\(-1\) - \
> \@5)\)\^3\)\(.\)\)\)
> {True, -1 + (1/2)*(-1 - Sqrt[5])^2 + (1/8)*(-1 - Sqrt[5])^3 == 0, -1 +
> (1/2)*(-1 + Sqrt[5])^2 + (1/8)*(-1 + Sqrt[5])^3 == 0}
> 
> which they don't avoid the verification
> 
> FullSimplify[%]
> {True,True,True}
> 
> Is it a way to avoid the messages (apart from turn off the message)?
> 
> The following seems not to help.
> 
> Block[{$MaxExtraPrecision = 1000}, x^3 + 2*x^2 - 1 == 0 /. sols]
> 
> Thanks a lot
> 

--

Bob Hanlon
hanlonr at cox.net



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