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Re: Simplify stuck in simple expression

• To: mathgroup at smc.vnet.net
• Subject: [mg50164] Re: Simplify stuck in simple expression
• From: carlos at colorado.edu (Carlos Felippa)
• Date: Wed, 18 Aug 2004 01:20:18 -0400 (EDT)
• References: <cfsi9a$a78$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Bob Hanlon <hanlonr at cox.net> wrote in message news:<cfsi9a$a78$1 at smc.vnet.net>...
> 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
> 
Unfortunately it isnt practical.  That expression is inside a deep
loop that solves thousands of quadratic equations, and the expressions
under Sqrt keep changing.   I just cooked up a simplified form for
posting.

Is there an equivalent of FactorTerms that can force a numerical
factor out of a symbolic square root?

• Follow-Ups:
  • Re: Re: Simplify stuck in simple expression
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>