Re: Bairstow Method

• To: mathgroup at smc.vnet.net
• Subject: [mg71801] Re: Bairstow Method
• From: Paul Abbott <paul at physics.uwa.edu.au>
• Date: Wed, 29 Nov 2006 02:56:52 -0500 (EST)
• Organization: The University of Western Australia
• References: <ej1qbe\$e45\$1@smc.vnet.net>

```In article <ej1qbe\$e45\$1 at smc.vnet.net>, "ms z" <ms-z- at hotmail.com>
wrote:

> I posted a question on how to write an automated program to solve the
> polynomial f(x)=(x-4)(x+2)(x-1)(x+5)(x-7) (without using NSolve or Solve)
> earlier on.
>
> I suggested this program: (though not a good one)
> solution := {Plot[{(x - 4)(x + 2)(x - 1)(x + 5)(x - 7)}, {x, -10, 10},
> AxesLabel -> TraditionalForm /@ {x, y}]}
>
> I've tried to write another program using Bairstow Method. But it doesn't
> not seem to work. Could I have some help?

Mathematica code for the Lin-Bairstow method is available at

http://math.fullerton.edu/mathews/n2003/BairstowMethodMod.html

Since Mathematica can already compute all the roots of univariate
polynomials, why do you need to use the Lin-Bairstow method? The
it avoids all complex arithmetic. However, FindRoot can find all complex
roots.

Cheers,
Paul

_______________________________________________________________________
Paul Abbott                                      Phone:  61 8 6488 2734
School of Physics, M013                            Fax: +61 8 6488 1014
The University of Western Australia         (CRICOS Provider No 00126G)
AUSTRALIA                               http://physics.uwa.edu.au/~paul

```

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