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MathGroup Archive 1996

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Re: Will you please help a non-mathematician?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg5606] Re: Will you please help a non-mathematician?
  • From: pecora at zoltar.nrl.navy.mil (Lou Pecora)
  • Date: Fri, 27 Dec 1996 23:43:38 -0500
  • Organization: Naval Research Lab
  • Sender: owner-wri-mathgroup at wolfram.com

In article <59vp4j$f82 at dragonfly.wolfram.com>, DONKROUS at HALCYON.COM (Don
Krouse) wrote:

> Please be gentle, I'm not a mathematician.
> 
> Solving the below equation for all variables, except i, works
> satisfactorily. Trying to solve for i produces the following result.
> 
> in[1] Solve[0==PV+PMT*((1-(1+i)^-n)/i)+FV*(1+i)^-n,i]
> 
> Solve::tdep: 
>    The equations appear to involve transcendental functions of
>     the variables in an essentially non-algebraic way.
> 
> out[1] Solve[0 == FV/(1 + i)^n + ((1 - (1 + i)^(-n))*PMT)/i + PV, i]
> 
> Can someone tell me how to get Mathematica to solve for i?

I think what MMA is telling you is that it _can't_ solve for i.  A quick
glance at your equation makes me think there is no algebraic solution. 
Typically, equations involving a variable _and_ exponentials of the
variable are unsolvable.  There are special case exceptions.  You really
need to find someone mathematical to look at your case and see if it can
be done.  Sorry, that wasn't much help.  The alternative is to use
numerical solutions.

Lou Pecora
code 6343
Naval Research Lab
Washington  DC  20375
USA
 == My views are not those of the U.S. Navy. ==

------------------------------------------------------------
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  http://natasha.umsl.edu/Exp_Chaos4/

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