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MathGroup Archive 2003

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AW: Emergent Help: NSolve Problems!

  • To: mathgroup at smc.vnet.net
  • Subject: [mg39823] AW: [mg39753] Emergent Help: NSolve Problems!
  • From: Matthias.Bode at oppenheim.de
  • Date: Sat, 8 Mar 2003 02:48:05 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Hello Chengzhou,

Version 4.1.1:
Input:
s^10 + 10 s^9 + 10 s^8 + 10 s^7 + 10 s^6 + 10 s^5 + 10 s^4 + 1 /. 
  s -> -8.999981180131652

Output:
-4.76837158203125*^-7

Acceptably close to zero?

Best regards,
Matthias Bode
Sal. Oppenheim jr. & Cie. KGaA
Koenigsberger Strasse 29
D-60487 Frankfurt am Main
GERMANY
Tel.: +49(0)69 71 34 53 80
Mobile: +49(0)172 6 74 95 77
Fax: +49(0)69 71 34 95 380
E-mail: matthias.bode at oppenheim.de
Internet: http://www.oppenheim.de




-----Ursprüngliche Nachricht-----
Von: Chengzhou Wang [mailto:wcz at ece.ucsd.edu]
Gesendet: Donnerstag, 6. März 2003 08:35
An: mathgroup at smc.vnet.net
Betreff: [mg39753] Emergent Help: NSolve Problems!


Hi, guys

I have some complicated polynomials, and I want to calculate its roots.
HOwever, when I use NSolve, it creates some problems. Say a simple
example:

temp[s_]=s^10+10 s^9+ 10 s^8 +10 s^7 +10 s^6+ 10 s^5 +10 s^4 +1; 
NSolve[temp[s]==0, s]

It will give:

Out[4]= {{s -> -8.99998}, {s -> -1.06539}, {s -> -0.468828 - 0.886239 I}, 
 
>    {s -> -0.468828 + 0.886239 I}, {s -> -0.409684 - 0.469948 I}, 
 
>    {s -> -0.409684 + 0.469948 I}, {s -> 0.401048 - 0.312597 I}, 
 
>    {s -> 0.401048 + 0.312597 I}, {s -> 0.51015 - 0.878693 I}, 
 
>    {s -> 0.51015 + 0.878693 I}}

But when I plug in the first number, which is "-8.99998", it should give a
value close to zero. However, it gives:

In[5]:= temp[-8.99998]
Out[5]= -411.473

The other roots seems OK. Does anyone know why? This is just a simple
example. I have some more complicated polynomials to deal with. 

Thanks in advance!

PS: Please reply (cc) to my email. I did not subscribe my email to the
this email group!

--
Chengzhou



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