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MathGroup Archive 2004

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Re: Problem with Mathematica driving me nuts

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46827] Re: Problem with Mathematica driving me nuts
  • From: Janusz Kawczak <jkawczak at math.uncc.edu>
  • Date: Tue, 9 Mar 2004 04:31:19 -0500 (EST)
  • References: <c2he1m$ahd$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Yes, the Newton's method is used. Why don't you try something
like Solve[] or

In[1]:=<< NumericalMath`InterpolateRoot`
In[2]:=InterpolateRoot[4 - 4 x + x^2 == 0, {x, 0, 1}, ShowProgress ->
False,
    WorkingPrecision -> 70, AccuracyGoal -> 65, MaxIterations -> 100]
Out[2]:={x -> 2.000000000000000000000000}

You can change ShowProgress -> False to True to see how it's calculated.

Janusz.

"benwoodward.com" wrote:

> FindRoot[x^2 == 4x - 4, {x, 1}]
>
> Out[4]=
> {x -> 1.99902}
>
> In[15]:=
> FindRoot[x^2 - 4*x + 4, {x, 3}]
>
> Out[15]=
> {x -> 2.00098}
>
> When the root is clearly two.
> Is Mathematica using Newton's Method like a Ti-92?
> Even if so, why wont it give a more accurate answer?
> I've tried N[%,30] but it doesn't do anything.
> I'm new to Mathematica coming over from a Ti-92, so everything is
> frustrating right now.
> Thanks.


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