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Student Support Forum: 'A problem with FindRoot' topicStudent Support Forum > General > "A problem with FindRoot"

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Vassilis
11/24/07 04:56am

Hi All,

I'd like some help with respect to a problem I have with the FindRoot, NSolve and FindInstance functions.
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? Needless to say, the actual problem
I try to tackle involves much more complicated functions...

Thanks,
Vassilis

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Subject (listing for 'A problem with FindRoot')
Author Date Posted
A problem with FindRoot Vassilis 11/24/07 04:56am
Re: A problem with FindRoot yehuda ben-s... 12/02/07 11:32am
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