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Topic: A Special Function
Replies: 6   Last Post: Aug 17, 2012 2:06 PM

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ksoileau

Posts: 85
From: Houston, TX
Registered: 3/9/08
Re: A Special Function
Posted: Aug 16, 2012 3:37 PM
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On Thursday, August 16, 2012 1:24:48 PM UTC-5, Virgil wrote:
> In article <79ef3761-e9ef-42c8-823b-a7e804d1fc95@googlegroups.com>,
>
> ksoileau wrote:
>
>
>

> > Hello All,
>
> > I'm looking for a real valued function f, continuous on R^n, for a given n,
>
> > such that f(x_1,x_2,...,x_n)>0 if and only if x_i>0 for each i=1,2,...,n.
>
> > Thanks!
>
> > Kerry M. Soileau
>
>
>
> Note that |x| + x > 0 if and only if x > 0, so
>
>
>
> f(x_1,...,x_n) =(|x_1| + x_1)*(|x_2| + x_2)*...*(|x_n| + x_n)
>
>
>
> fits your requirements
>
> --


Nice, thanks!



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