Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2004
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2004

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Number of roots from Solve?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg48443] Re: [mg48423] Number of roots from Solve?
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Sun, 30 May 2004 06:12:04 -0400 (EDT)
  • References: <200405290706.DAA20383@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

I think having inexact coefficients does not make any difference here 
since I am pretty sure Solve first applies Rationalize to everything. 
In fact I don&t think it would not make any sense to do otherwise, 
given that Solve uses only algebraic and not numerical techniques. 
Since the equations are non-polynomial I can see nothing at all strange 
about them having very different numbers of roots.

Andrzej Kozlowski


Since the equation is non-polynomial I do not see an

On 29 May 2004, at 16:06, Goyder Dr HGD wrote:

> I am working with the expression
>
> a =.; b =.; e = (1/z)((2 + z^2 (b - 1))/(b + 1))^((1 + b)/(2(b - 1)))
>
> and was not surprised to find a number of complex and real roots (6)  
> for
> the particular case
>
> a = 10.; b = 1.4; s = Solve[a == e]; {Length[s], s}
>
> I was surprised that the number of roots changed to 41 for the case
>
> a = 10.; b = 1.05; s = Solve[a == e]; {Length[s], s}
>
> With
>
> a = 10.; b = 1.03; s = Solve[a == e]; {Length[s], s}
>
> I never got an answer (or the calculation takes longer than my 
> patience).
>
> Is it possible to predict the number of roots that an expression like e
> above will produce?
> Does Mathematica find all the roots, particularly as we are dealing 
> with
> approximate numbers?
>
> Many thanks
>
> Hugh Goyder
>
> -- 
> This message has been scanned for viruses and
> dangerous content by the Cranfield MailScanner, and is
> believed to be clean.
>
>


  • Prev by Date: Eigensystem[] bug in Mathematica 5.0 (fixed in 5.0.1)
  • Next by Date: Re: how can I solve a function Erfc
  • Previous by thread: Number of roots from Solve?
  • Next by thread: Re: Number of roots from Solve?