MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

solving simple first order condition

  • To: mathgroup at
  • Subject: [mg54050] solving simple first order condition
  • From: juejung <juejung at>
  • Date: Wed, 9 Feb 2005 09:27:22 -0500 (EST)
  • Sender: owner-wri-mathgroup at

Hi all,

I have the following problem with a simple First Order Condition (FOC) out  
of an OLG model in Economics.

u[c_] := c^(1 - sigma)/(1 - sigma);
Ts[x_] := theta*x;
maxFun[se_] := u[(1 - tau)*w - s] + beta*u[R*s + Ts[R*s]];
der = FullSimplify[D[maxFun[s], s]]
sol = Solve[{der == 0}, {s}]

Why can't Mathematica solve this simple FOC when I can do it so easily by  

If I use the FOC and replace the (1+theta) by Theta (capital theta) and do  
the same Solve command, then it works (as shown in sol1 below) and I can  
get a closed form solution.

sol1 = Solve[{(beta*R*Theta)/(R*s*Theta)^sigma -
       (-s + w - tau*w)^(-sigma) == 0}, {s}]

I find it annoying that I apparently have to replace all (1+something)  
expressions by a single variable (easy here, but cumbersome in more  
involved models). Is there an easy simplify command hidden somewhere??

Juergen Jung
Indiana University
Bloomington, US

Using Opera's revolutionary e-mail client:

  • Prev by Date: Re: Fourier function...having problems reproducing answers in a paper
  • Next by Date: Re: Summary: Which[] as Textbook Input, Plot[] Questions
  • Previous by thread: Re: Re: how to have a blind factorization of a polinomial?
  • Next by thread: finding package in ExtraPackages`Enhancements`