Re: Find a single solution to a system of equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg121852] Re: Find a single solution to a system of equations*From*: Peter Pein <petsie at dordos.net>*Date*: Wed, 5 Oct 2011 03:59:51 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j6e648$kd6$1@smc.vnet.net>

Am 04.10.2011 07:38, schrieb jamievicary at NgOmSaPiAlM.com: > Hi, > > I have a system of equations, and want to use Mathematica to find a > single solution. It's no good using Solve, because then Mathematica > tries to find all solutions, and that takes too long. It's no good > containing FindInstance, because my equations contain unknowns. > > To illustrate this last point, consider the input > FindInstance[a==b,a] > I want Mathematica to return to me the solution > {{a->b}} > but it doesn't -- it fails, because FindInstance can't cope with > independent variables in the expression. > > So, I either need a watered-down Solve, that doesn't try to find every > solution, or a beefed-up FindInstance, that doesn't mind about the > independent variables. > > Thanks! > Jamie. > There is a trick in [1] (by Peter Valko). Replace b by a constant not related to your problem, apply FindInstance and substitute the chosen constant with b: In[1]:= FindInstance[{a == b} /. b -> Catalan, a] /. Catalan -> b Out[1]= {{a->b}} Peter [1] http://forums.wolfram.com/mathgroup/archive/2006/Sep/msg00207.html