Re: domain restriction in NSolve does not work
- To: mathgroup at smc.vnet.net
- Subject: [mg128873] Re: domain restriction in NSolve does not work
- From: Bob Hanlon <hanlonr357 at gmail.com>
- Date: Sat, 1 Dec 2012 04:36:30 -0500 (EST)
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- Delivered-to: l-mathgroup@wolfram.com
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- References: <20121130105645.775586898@smc.vnet.net>
I believe that this capability was added starting with version 8.
NSolve[x^5 - 2 x + 3 == 0, x, Reals]
{{x -> -1.42361}}
Works on my Mac with either version 8 or 9. You can also use
Select[NSolve[x^5 - 2 x + 3 == 0, x],
FreeQ[#, Complex] &]
{{x -> -1.42361}}
Select[NSolve[x^5 - 2 x + 3 == 0, x],
Element[x /. #, Reals] &]
{{x -> -1.42361}}
Select[NSolve[x^5 - 2 x + 3 == 0, x],
Element[#[[1, -1]], Reals] &]
{{x -> -1.42361}}
Bob Hanlon
On Fri, Nov 30, 2012 at 5:56 AM, <niieldo at googlemail.com> wrote:
> Dear all,
>
> I have encountered the problem that restricting domains in NSolve does not work.
> I get the same results for NSolve[x^5 - 2 x + 3 == 0, x, Reals] as with NSolve[x^5 - 2 x + 3 == 0, x], namely {{x -> -1.42361}, {x -> -0.246729 - 1.32082 I}, {x -> -0.246729 +
> 1.32082 I}, {x -> 0.958532 - 0.498428 I}, {x ->
> 0.958532 + 0.498428 I}}
>
> I.e. Mathematica actually does not apply the restriction.
>
> Does anyone have a solution for this? Do I have to adjust the settings somewhere?
>
> many thanks in advance
> Niels
>
>