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Re: rearrange tough explicit equation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg130684] Re: rearrange tough explicit equation
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Wed, 1 May 2013 21:42:11 -0400 (EDT)
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On 5/1/13 at 3:35 AM, davejamesbrackett at gmail.com (db) wrote:

>Hi, I'm trying to rearrange to isolate V in this equation, but am
>having trouble working out the right way to tackle it. Could someone
>give me some help in how to approach this? Thanks a lot.

>Rearrange to isolate V: A = 10^(K*(e^(c_1*V))+(e^(c_2*V)))

You have several problems:

Don't use single uppercase letters as variables. Many of these
have pre-defined values in Mathematica. If you use single
uppercase letters as variables you are likely to run into a
conflict and get results you didn't expect.

I assume e^c is meant to be Exp[c] which can be entered as E^c.
e is an undefined symbol. E is 2.718...

You cannot create subscripted variables as c_1 in Mathematica.
It is possible to use subscripted variables in Mathematica. But
this isn't made easy and requires the notation package to work correctly.

Finally, assuming you meant to do:

a = 10^(k*(E^(c1*v)) + (E^(c2*v)))

There is no closed form general solution for v since it appears
in exponentials and is multiplied by different values. The only
closed form solution for v occurs in the special case where c1
== c2.

That is:

eq=a == 10^(k*(E^(c1*v)) + (E^(c2*v))) /. {c1 -> c, c2 -> c}
Solve[eq,v]

Will produce a result




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