Re: Selecting Real Roots, Again
- To: mathgroup at smc.vnet.net
- Subject: [mg67174] Re: Selecting Real Roots, Again
- From: David Bailey <dave at Remove_Thisdbailey.co.uk>
- Date: Sun, 11 Jun 2006 02:18:10 -0400 (EDT)
- References: <e6b5q5$d3c$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hello, If you execute Solve[.9 x^10 + .1 x^2 ==y,x] you get a set of Root expressions because beyond order 4 symbolic polynomial equations such as this do not have solutions (except in terms of some impossibly complicated expressions involving Hypergeometrics or Theta functions). See for example: http://library.wolfram.com/examples/quintic/main.html Given that you don't have any answers, I can't see how you can filter them to select the Real ones! Note that you could, of course, solve this equation numerically if you gave y a value - then you could use the methods previously discussed to eliminate the imaginary roots. David Bailey http://www.dbaileyconsultancy.co.uk