Re: Solve with assumptions

*To*: mathgroup at smc.vnet.net*Subject*: [mg57808] Re: Solve with assumptions*From*: dh <dh at metrohm.ch>*Date*: Thu, 9 Jun 2005 05:17:41 -0400 (EDT)*References*: <d86937$c7n$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi Muktar, try e.g. Reduce. Here is a small example. Reduce[{x^3 + 1 == 0}, x] gives x == -1 || x == (-1)^(1/3) || x == -(-1)^(2/3) on real and two complex solutions. However: Reduce[{Element[x, Reals], x^3 + 1 == 0}, x] gives x == -1 or another example: Reduce[{x < 0, x^2 - 1 == 0}, x] sincerely, Daniel Mukhtar Bekkali wrote: > I need to solve equation f[x1,x2] for x1 and x2, where I know that x1>0 > and x2>0 and are both real. Solve[f[x1,x2]==0,{x1,x2}] takes a lot of > time to solve and when it does solve it gives me tons of unreal > solutions or repetitive solutions (I have enabled Miscellanous RealOnly > and instead of complex solutions it just gives me Unreal). I would > like to know how I (1) can restrict the solution set where Mathematica > is trying to find a solution, and (2) show only unique solutions and > totally not showing Unreal ones. FindRoot is great but it is very > dependent on starting values which is not good for me. Thankx, Mukhtar > Bekkali >