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Re: Re: Re: How to solve nonlinear equations?


Neither of us has answered the original question, which was "How to solve...".

Let's say we need 200 digits. How do you solve it?

Bobby

On Fri, 3 Dec 2004 03:53:43 -0500 (EST), Jens-Peer Kuska <kuska at informatik.uni-leipzig.de> wrote:

> Hi,
>
> the problem will never solved by  Mathematica
> when the input uses a invalid syntax and the original posting
> say nothing about the desired precision. But from the
> equations it is easy to see that one nneds several hundred
> digits.
>
> Regards
>   Jens
>
> "DrBob" <drbob at bigfoot.com> schrieb im Newsbeitrag
> news:comgo1$89e$1 at smc.vnet.net...
>> The only trouble with THAT is that it doesn't work.
>>
>> eqns = {20.428836553499018 - Log[X1] == 468/67*X1 + 5790/1273*X2 -
>> 66257/1273*
>>         X3 - 24660/1273*X4 - 79150/1273*X5, 17.011108423692498 -
>>            Log[X2] == 5790/1273*X1 + 6294/1273*X2 - 66257/1273*X3 - 24660/
>>           1273*X4 - 403.8069285*
>>             X5, -29.72639373695347 - Log[X3] == -66257/1273*
>>           X1 - 66257/1273*X2 - 2*
>>         X3, -26.273726271581616 - Log[X4] == -24660/1273*X1 - 24660/
>>           1273*X2 + 10.15330715*X4, -38.76695085346396 - Log[X5]
>> == -79150/
>>           1273*X1 - 403.8069285*X2 - 10.67374705*X5};
>>
>> FindRoot[eqns, {{X1, 1}, {X2, 1}, {X3, 1}, {X4, 1}, {X5, 1}}]
>> eqns /. Equal -> Subtract /. %
>>
>> (FindRoot::lstol error)
>> {X1 -> 0.5287215008048355 + 0.0078093799604902845*I,
>>   X2 -> 0.002514442570050682 - 0.007506800892680369*I,
>>   X3 -> 0.2750175495952261 + 0.0051666476248725625*I,
>>   X4 -> -1.6157105189511614 -4.778719413301337*^-15*I,
>>   X5 -> -0.006058532522555838 - 0.003759309847863656*I}
>> {-0.0000172993518866571 - 5.25106242902848*^-7*I,
>>   0.0014397436481736747 + 0.000060457451791506855*I,
>>   -0.23588972784670026 + 0.007297504899863284*I,
>>   -0.057825246363192695 + 3.1474540831359445*I,
>>   0.0009303265262765592 + 0.00036856201666024546*I}
>>
>> Bobby
>>
>> On Wed, 1 Dec 2004 05:57:41 -0500 (EST), Jens-Peer Kuska
>> <kuska at informatik.uni-leipzig.de> wrote:
>>
>>> Hi,
>>>
>>> a) learn the correct syntax of Mathematica
>>> b) read the Mathematica book carefully
>>> c) type:
>>>
>>> eqns = {20.428836553499018 - Log[X1] ==
>>> 468/67*X1 + 5790/1273*X2 - 66257/1273*X3 - 24660/1273*X4 -
>>> 79150/1273*X5,
>>> 17.011108423692498 - Log[X2] ==
>>> 5790/1273*X1 + 6294/1273*X2 - 66257/1273*X3 - 24660/1273*X4 -
>>> 403.8069285*X5, -29.72639373695347 - Log[X3] == -66257/1273*X1 -
>>> 66257/1273*X2 - 2*X3, -26.273726271581616 -
>>> Log[X4] == -24660/1273*X1 - 24660/1273*X2 +
>>> 10.15330715*X4, -38.76695085346396 - Log[X5] == -79150/1273*X1 -
>>> 403.8069285*X2 - 10.67374705*X5}
>>>
>>> FindRoot[eqns, {{X1, 1}, {X2, 1}, {X3, 1}, {X4, 1}, {X5, 1}}]
>>>
>>>
>>>
>>> Regards
>>>
>>>   Jens
>>>
>>>
>>> "Wei Wang" <weiwang at baosteel.com> schrieb im Newsbeitrag
>>> news:cohj9d$1nr$1 at smc.vnet.net...
>>>> How to solve the following equations, where X1, X2, X3, X4 and X5 are
>>>> variables?
>>>>
>>>> eqns = {20.428836553499018-ln(X1) ==
>>>> 468/67*X1+5790/1273*X2-66257/1273*X3-24660/1273*X4-79150/1273*X5,
>>>> 17.011108423692498-ln(X2) ==
>>>> 5790/1273*X1+6294/1273*X2-66257/1273*X3-24660/1273*X4-403.8069285*X5, -29.72639373695347-ln(X3)
>>>> == -66257/1273*X1-66257/1273*X2-2*X3, -26.273726271581616-ln(X4)
>>>> == -24660/1273*X1-24660/1273*X2+10.15330715*X4, -38.76695085346396-ln(X5)
>>>> == -79150/1273*X1-403.8069285*X2-10.67374705*X5};
>>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>> --
>> DrBob at bigfoot.com
>> www.eclecticdreams.net
>>
>
>
>
>
>



-- 
DrBob at bigfoot.com
www.eclecticdreams.net


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