[Q] Solve?

*To*: mathgroup at smc.vnet.net*Subject*: [mg23408] [Q] Solve?*From*: research at proton.csl.uiuc.edu (James)*Date*: Sat, 6 May 2000 19:14:15 -0400 (EDT)*Organization*: University of Illinois at Urbana-Champaign*Sender*: owner-wri-mathgroup at wolfram.com

Hi! I come across a problem that I don't understand. I generate systems of equations and try to solve them using mathematica. For example, --------------------------------------------------------------- In[1]= Solve[((4/2)*( 1.50*z+ 2.00)+(4-4/2)* Sqrt[( 1.50*z+ 0.00)^2+ 4.00]) + ((4/2)*( 1.50*z+ 2.00)+(4-4/2)* Sqrt[( 1.50*z+ 0.00)^2+ 4.00])- 8.10*z==0, z] Out[1]= {} --------------------------------------------------------------- But mathematica can't solve it, simply returing empty. This equation can be solved, though, as you see. I restarted mathematica to run again, but it doesn't help. The weird thing is some equations are solved, like the below. --------------------------------------------------------------- In[2]= Solve[((4/2)*( 1.50*z+ 2.00)+(2-4/2)* Sqrt[( 1.50*z+ 0.00)^2+ 4.00]) + ((4/2)*( 1.50*z+ 2.00)+(3-4/2)* Sqrt[( 1.50*z+ 0.00)^2+ 4.00])- 8.10*z==0, z] Out[2]= {{z->13.4976}} --------------------------------------------------------------- What's wrong with it and how can I solve it? I need to use mathematica, because the number of the systems of equations are large. (Please disregard any redundunt terms in the equations.. they are generated by a program.) With that, when does mathematica return '{}' as an answer? Thank you. --- James, newbie in mathematica.