Re: Solve[] doesn't

*To*: mathgroup at smc.vnet.net*Subject*: [mg90631] Re: Solve[] doesn't*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Thu, 17 Jul 2008 05:33:30 -0400 (EDT)*Organization*: The Open University, Milton Keynes, UK*References*: <g5kil1$8lf$1@smc.vnet.net>

Hauke Reddmann wrote: > This is extremely annoying. > I have a very large (this seems to be critical) equation > system. It's partly linear, partly horror, but already > after I solve the linear part, a certain solution (which > is obviously one since substituting it in makes all equations > identical zero) can't be found anymore. The solution has some > surds (this also seems critical, the ones without are found) > but the equations are strictly polynomic. > > Faked Example (the real one only PM-ed, since it's a bit > oversized): > > x-y=1 > x^2+y^2=3 > x^3-y^3=4 > and after y was eliminated, it doesn't find x. (=golden mean here) > > Huh? Hum, I might not have understood correctly your problem really is, but my interpretation of your example works fine on my system (i.e. Solve[] returns the correct values for y *and* x): In[1]:= sys = {x - y == 1, x^2 + y^2 == 3, x^3 - y^3 == 4}; sols = Solve[sys] sys /. sols Out[2]= 1 1 {{x -> - (1 - Sqrt[5]), y -> - (-1 - Sqrt[5])}, 2 2 1 1 {x -> - (1 + Sqrt[5]), y -> - (-1 + Sqrt[5])}} 2 2 Out[3]= {{True, True, True}, {True, True, True}} In[4]:= $Version Out[4]= 6.0 for Mac OS X x86 (64-bit) (May 21, 2008) Regards, -- Jean-Marc