Re: Emergent Help: NSolve Problems!

*To*: mathgroup at smc.vnet.net*Subject*: [mg39790] Re: [mg39753] Emergent Help: NSolve Problems!*From*: Dr Bob <drbob at bigfoot.com>*Date*: Fri, 7 Mar 2003 03:38:51 -0500 (EST)*References*: <200303060735.CAA09182@smc.vnet.net>*Reply-to*: drbob at bigfoot.com*Sender*: owner-wri-mathgroup at wolfram.com

It's a precision problem. The first solution isn't -8.99998: temp[s_] = s^10 + 10 s^9 + 10 s^8 + 10 s^7 + 10 s^6 + 10 s^5 + 10 s^4 + 1; NSolve[temp[s] == 0, s] NumberForm[First@%, 20] temp[s] /. % temp[-8.99998] temp[-8.99998118013165] Bobby On Thu, 6 Mar 2003 02:35:04 -0500 (EST), Chengzhou Wang <wcz at ece.ucsd.edu> wrote: > Hi, guys > > I have some complicated polynomials, and I want to calculate its roots. > HOwever, when I use NSolve, it creates some problems. Say a simple > example: > > temp[s_]=s^10+10 s^9+ 10 s^8 +10 s^7 +10 s^6+ 10 s^5 +10 s^4 +1; > NSolve[temp[s]==0, s] > > It will give: > > Out[4]= {{s -> -8.99998}, {s -> -1.06539}, {s -> -0.468828 - 0.886239 I}, > >> {s -> -0.468828 + 0.886239 I}, {s -> -0.409684 - 0.469948 I}, > >> {s -> -0.409684 + 0.469948 I}, {s -> 0.401048 - 0.312597 I}, > >> {s -> 0.401048 + 0.312597 I}, {s -> 0.51015 - 0.878693 I}, > >> {s -> 0.51015 + 0.878693 I}} > > But when I plug in the first number, which is "-8.99998", it should give > a > value close to zero. However, it gives: > > In[5]:= temp[-8.99998] > Out[5]= -411.473 > > The other roots seems OK. Does anyone know why? This is just a simple > example. I have some more complicated polynomials to deal with. > > Thanks in advance! > > PS: Please reply (cc) to my email. I did not subscribe my email to the > this email group! > > -- > Chengzhou > > > -- majort at cox-internet.com Bobby R. Treat

**References**:**Emergent Help: NSolve Problems!***From:*Chengzhou Wang <wcz@ece.ucsd.edu>