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MathGroup Archive 2006

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Re: solving an equation with sums

  • To: mathgroup at smc.vnet.net
  • Subject: [mg67487] Re: solving an equation with sums
  • From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
  • Date: Wed, 28 Jun 2006 03:51:36 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <e7qmi0$6lb$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

FindRoot[] may help you.

Regards
  Jens

<newbix at bk.ru> schrieb im Newsbeitrag 
news:e7qmi0$6lb$1 at smc.vnet.net...
| Hello,
|
| I try to solve the following equation:
| 
sum[2*(1-e^(-x*t[[i]])-F[[i]])*t[[i]]*e^(-x*t[[i]]),{i,1,10}]==0
| where t and F are lists. Each list has ten 
entries.
| I tried to solve this sum using the following 
command:
| ------------------------------------------------------
| Solve[2*(1 - \[ExponentialE]^(-x*0.1) - 
2810)*0.1*\[ExponentialE]^(-x*0.1) +
|      2*(1 - \[ExponentialE]^(-x*0.2) - 
5411)*0.2*\[ExponentialE]^(-x*0.2) +
|      2*(1 - \[ExponentialE]^(-x*0.3) - 
8701)*0.3*\[ExponentialE]^(-x*0.3) +
|      2*(1 - \[ExponentialE]^(-x*0.4) - 
13130)*0.4*\[ExponentialE]^(-x*0.4) +
|      2*(1 - \[ExponentialE]^(-x*0.5) - 
17327)*0.5*\[ExponentialE]^(-x*0.5) +
|      2*(1 - \[ExponentialE]^(-x*0.6) - 
24899)*0.6*\[ExponentialE]^(-x*0.6) +
|      2*(1 - \[ExponentialE]^(-x*0.7) - 
31230)*0.7*\[ExponentialE]^(-x*0.7) +
|      2*(1 - \[ExponentialE]^(-x*0.7) - 
40006)*0.8*\[ExponentialE]^(-x*0.8) +
|      2*(1 - \[ExponentialE]^(-x*0.8) - 
59880)*0.9*\[ExponentialE]^(-x*0.9) +
|      2*(1 - \[ExponentialE]^(-x) - 
80017)*\[ExponentialE]^(-x) == 0, x]
| -----------------------------------------
| but I got the following error message:
|
| Solve::"tdep": "The equations appear to involve 
the variables to be solved \
| for in an essentially non-algebraic way."
|
| What's wrong? How can I solve this expression 
using Mathematica?
|
| Thank you in advance!
| 



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