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Re: Why is the negative root?


Hi,

(Reduce[{z^3 - z^2 - b z - 1 == 0, b > 0, z > 0}, 
z] // ToRadicals) /.
b -> 3 // FullSimplify

gives

Sqrt[2]+z==1

And you should be more careful when you use // to 
apply

functions and look in what order the functions are 
used.

Regards

  Jens

<p-valko at tamu.edu> schrieb im Newsbeitrag 
news:ee8h8v$j48$1 at smc.vnet.net...
| (Reduce[{z^3-z^2- b z-1==0, b>0, z>0}, z] 
//ToRadicals)/.b->3.//Chop
|
| gives a negativ z:
|
| z == - 0.414214
|
| What am I doing wrong?
|
| Regards
| Peter
| 



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