Re: extract only positive solutions

*To*: mathgroup at smc.vnet.net*Subject*: [mg125047] Re: extract only positive solutions*From*: Helen Read <readhpr at gmail.com>*Date*: Sun, 19 Feb 2012 06:32:53 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <jhldd0$oql$1@smc.vnet.net>

On 2/17/2012 6:24 AM, Gabby Domingo wrote: > hi all! how do you extract only positive solutions to a solver, like > NSolve? > > sol={{-.532,.932},{.34,23}} > > and extract {.34,.23}? > You can restrict the domain in Solve. For example: f[x_]:=150 - 15 x - 50 x^2 + 2 x^3 - 6 x^4 + x^5 + 2 x^6 Solve[f[x]==0,x] Solve[f[x]==0,x,Reals] Solve[f[x]==0,x,Rationals] Solve[f[x]==0,x,Integers] Solve[f[x] == 0 && x > 0, x] So if I understand what you are trying to do, something like this: {x, y} /. Solve[{y == x^2 - 2 x - 5, y == 7 - x, x > 0, y > 0}, {x, y}] -- Helen Read University of Vermont