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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: [mg46799] Re: Problem with Mathematica driving me nuts
  • From: bobhanlon at aol.com (Bob Hanlon)
  • Date: Tue, 9 Mar 2004 04:30:42 -0500 (EST)
  • References: <c2he1m$ahd$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Check your options settings.

$Version

"5.0 for Mac OS X (November 19, 2003)"

FindRoot[x^2 == 4x - 4, {x, 1}]

{x -> 1.9999999701976776}

FindRoot[x^2 - 4*x + 4, {x, 3}]

{x -> 2.0000000298023224}

FindRoot[x^2 == 4x - 4, {x, 1}, WorkingPrecision->30]

{x -> 
   1.999999999999996447286321199499070644378662109375`30.}


Bob Hanlon

In article <c2he1m$ahd$1 at smc.vnet.net>, bpw67deletethis at hotmail.com
(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.


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