Re: Problem with Mathematica driving me nuts
- To: mathgroup at smc.vnet.net
- Subject: [mg46825] Re: [mg46791] Problem with Mathematica driving me nuts
- From: Tomas Garza <tgarza01 at prodigy.net.mx>
- Date: Tue, 9 Mar 2004 04:31:16 -0500 (EST)
- References: <200403080910.EAA10442@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Unable to reproduce your results. I'm using Version 5.0.1 under Windows XP.
Of course, you'll never get x->2, since Mathematica uses a numerical method
(see Implementation Notes in the Help Browser: Polynomial root finding is
done based on the Jenkins-Traub algorithm). My approximation is better than
yours, anyway:
In[1]:=
FindRoot[x^2 == 4*x - 4, {x, 1}]
Out[1]=
{x -> 1.9999999701976776}
In[2]:=
FindRoot[x^2 - 4*x + 4, {x, 3}]
Out[2]=
{x -> 2.0000000298023224}
In this case, however, you may try Solve:
In[3]:=
Solve[x^2 == 4*x - 4, x]
Out[3]=
{{x -> 2}, {x -> 2}}
Tomas Garza
Mexico City
----- Original Message -----
From: "benwoodward.com" <bpw67deletethis at hotmail.com>
To: mathgroup at smc.vnet.net
Subject: [mg46825] [mg46791] Problem with Mathematica driving me nuts
> 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.
>
>
- References:
- Problem with Mathematica driving me nuts
- From: bpw67deletethis@hotmail.com (benwoodward.com)
- Problem with Mathematica driving me nuts