Solving equations / real valued variables and parameters

*To*: mathgroup at smc.vnet.net*Subject*: [mg33985] Solving equations / real valued variables and parameters*From*: hannes.egli at uni-greifswald.de (Hannes Egli)*Date*: Thu, 25 Apr 2002 03:00:07 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Hi I have got two questions. (1) If I try to solve the following equation for "m". Solve[a/(a+b+n)-(a+b+n)*((a/(a+b+n))^a)*(((b+n)/(a+b+n))^(b+n))*m^(a+b+n-1) = = 0, m] I receive the error message "The equations appear to involve the variables to be solved for in an essentially non-algebraic way". However, if I set n=0, Solve[a/(a+b)-(a+b)*((a/(a+b))^a)*((b/(a+b))^b)*m^(a+b-1) = = 0, m] Mathematica gives me a solution for "m". m -> ((((a/(a+b))^a)*((b/(a+b))^b)*(a+b)^2)/a)^(1/(1-a-b)) I do not understand, why Mathematica does not give me a solution for the first equation, since both equations look very similar. (2) My second question concerns real valued variables/parameters. Is there a possibility to tell Mathematica (at the beginning of a notebook file or within a function) that some variables and/or parameters are real valued? Thanks for your answers Hannes