Re: System for which Solve and NSolve both fail

*To*: mathgroup at smc.vnet.net*Subject*: [mg30573] Re: System for which Solve and NSolve both fail*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Thu, 30 Aug 2001 03:51:20 -0400 (EDT)*References*: <9mi1rt$54r$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Ben, Both Solve and NSolve are primarilly for polynomial equations. We can, of course, use FindRoot[{3^x + 3^y == 90,x + y == 6},{x,1},{y,2}] {x->2.,y->4.} -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "Ben Langton" <ben at spam.bugs.me.quickmath.com> wrote in message news:9mi1rt$54r$1 at smc.vnet.net... > Hi, > > I noticed that Mathematica seems unable to solve this system of equations : > > 3^x + 3^y = 90 > > x + y = 6 > > With a bit of thought, you can see by inspection that the solutions are > > {x , y} = {2 , 4} or {4 , 2} > > However, when I use the commands > > Solve[{3^x+3^y==90,x+y==6},{x,y}] > > or > > NSolve[{3^x+3^y==90,x+y==6},{x,y}] > > I get a warning message starting with > > Solve::incnst: Inconsistent or redundant transcendental equation > > Can anyone shed some light on what is going on here? Any way to get around > this problem? > > (I am using Mathematica v 3.0.0.0 under Mac OS 9.2.1, although I believe a > similar thing occurs under v 4.x) > > Regards, > > Ben Langton > > http://www.quickmath.com/ >