A problem with FindRoot

*To*: mathgroup at smc.vnet.net*Subject*: [mg83728] A problem with FindRoot*From*: Vassilis Dimitrakas <vdimitrakas at googlemail.com>*Date*: Thu, 29 Nov 2007 06:24:03 -0500 (EST)

Hi All, I'd like some help with respect to a problem I have with the FindRoot, NSolve and FindInstance functions. My version of Mathematica is 5.2 I define the function f as follows: f[x_]:={ y/.FindRoot[y^3+1==x,{y,x}][[1]] }[[1]] f[x] returns the root of the equation y^3 + 1 == x, i.e. the value (x-1)^(1/3). f[x] has obviously a unique root at x=1. If I now try to find f[x]'s root with FindRoot, for example like FindRoot[f[x]==0,{x,3}] Mathematica (v 5.2) returns error messages and no solution. The same happens if I use instead NSolve or FindInstance. Can you guys explain why this happens and suggest a remedy? Thanks, Vassilis

**Follow-Ups**:**Re: A problem with FindRoot***From:*Murray Eisenberg <murray@math.umass.edu>