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MathGroup Archive 2002

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Re: Intersection of sets of results

  • To: mathgroup at smc.vnet.net
  • Subject: [mg37115] Re: Intersection of sets of results
  • From: "Steve Luttrell" <luttrell at _removemefirst_westmal.demon.co.uk>
  • Date: Thu, 10 Oct 2002 03:20:51 -0400 (EDT)
  • References: <ao0tje$gs9$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Here is a way of doing what you want (output cells are indented):

<<"Algebra`InequalitySolve`"

x[n_]:=2331+8 n
y[n_]:=-3108-11 n

soln=InequalitySolve[{x[n]>=0,y[n]>=0},n]

    -(2331/8) <= n <= -(3108/11)

FullForm[soln]

    Inequality[Rational[-2331,8],LessEqual,n,LessEqual,Rational[-3108,11]]

Range[Apply[Sequence,{Ceiling[soln[[1]]],Floor[soln[[-1]]]}]]

    {-291, -290, -289, -288, -287, -286, -285, -284, -283}


--
Steve Luttrell
West Malvern, UK
email: luttrell at westmal.demon.co.uk


"flip" <flip_alpha at safebunch.com> wrote in message
news:ao0tje$gs9$1 at smc.vnet.net...
> Hello All,
>
> I have two equations that I have solved for:
>
> x[n_]  := 2331 + 8 n
> y[n_] :=  -3108 - 11n
>
> I want to include only solutions which are non-negative, that is x >= 0
and
> y >= 0.
>
> In this example we can do 2331 + 8n > = 0 and solve for n, n >= -291.375
> and -3108 - 11 n >= 0 and solve for n, n <= -282.545
>
> So we have -291.375 <= n <= -282.545.
>
> The "integer solution set here is for n =
> {-290, -289, -288, -287, -286, -285, -284, -283}.
>
> So in this case we have 8 non-negative solutions.
>
> Given that I can supply x[n] and y[n], how do I go about finding the set
n?
>
> Thank you for any inputs, Flip
>
>
>




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