Re: Why is the negative root?

*To*: mathgroup at smc.vnet.net*Subject*: [mg69491] Re: Why is the negative root?*From*: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>*Date*: Thu, 14 Sep 2006 06:55:22 -0400 (EDT)*Organization*: Uni Leipzig*References*: <ee8h8v$j48$1@smc.vnet.net>

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 |