Re: Simplify stuck in simple expression
- To: mathgroup at smc.vnet.net
- Subject: [mg50143] Re: [mg50127] Simplify stuck in simple expression
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Tue, 17 Aug 2004 05:01:24 -0400 (EDT)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
expr = (2-Sqrt[72*(1+a*b)^2+4])/(2*a); You can work around the problem by using a temporary change in variables (x = a*b + 1) Simplify[expr /. b-> (x-1)/a] /. x->a*b+1 or Simplify[expr /. a-> (x-1)/b] /. x->a*b+1 // Cancel Bob Hanlon > > From: carlos at colorado.edu (Carlos Felippa) To: mathgroup at smc.vnet.net > Date: 2004/08/16 Mon AM 06:45:34 EDT > To: mathgroup at smc.vnet.net > Subject: [mg50143] [mg50127] Simplify stuck in simple expression > > Hi - I wonder why > > Simplify[(2 - Sqrt[72*(1+a*b)^2+4])/(2*a)]; > > in v. 4.2 gets stuck. It does not reduce the expression to > > (1 - Sqrt[18*(1+a*b)^2+1])/a; > > FullSimplify and declaring-variable-attribute variations do not > work. What is necessary for the simplification to happen? > >