Re: NSolve
- To: mathgroup at smc.vnet.net
- Subject: [mg8631] Re: NSolve
- From: Daniel Lichtblau <danl>
- Date: Fri, 12 Sep 1997 04:10:45 -0400
- Organization: Wolfram Research, Inc.
- Sender: owner-wri-mathgroup at wolfram.com
(Fred Lang) wrote:
>
> Dear Mathgroupers,
>
> I've found something strange with NSolve in Mma 3.0 (PC and MAC).
>
> Try the following input:
>
> In[1] = NSolve[ x^2 + x(z+1) == 0 , x]
>
> Out[1] = {{x -> -1.},{x -> 0.}}
>
> In[2] = NSolve[x^2 + x z + x == 0 , x]
>
> Out[2] = {{x -> 0.},{x -> -1. - 1.z }}
>
> The first output is wrong. NSolve has choosen for me to put z = 0.
>
> OK! NSolve is a numerical command and z has no numerical value, but
>
> why don't NSolve give me something like "No numerical value for z, I put z
> = 0" ?
>
> In Mma 2.2, NSolve gives the correct answer.
>
> Thank you for your remarks.
>
> Cheers.
>
> Fred Lang
Small glitch, fixed in version 3.0.1. A work-around in version 3.0 would
be N[Solve[...]]. This is reasonable because, as you note, nothing
usefyul can be done with inexact methods because we have a non-numerical
parameter anyway.
Daniel Lichtblau
Wolfram Research
danl at wolfram.com