Re: Re: Simplify stuck in simple expression

*To*: mathgroup at smc.vnet.net*Subject*: [mg50171] Re: [mg50164] Re: Simplify stuck in simple expression*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Wed, 18 Aug 2004 04:34:07 -0400 (EDT)*References*: <cfsi9a$a78$1@smc.vnet.net> <200408180520.BAA06011@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

You can use: FullSimplify[Factor //@ ((2 - Sqrt[72*(1 + a*b)^2 + 4])/ (2*a))] (1 - Sqrt[18*a*b*(a*b + 2) + 19])/a However, as this has the same LeafCount as the expression you desire you, would need to find a suitable ComplexityFunction to obtain the answer you want. On 18 Aug 2004, at 07:20, Carlos Felippa wrote: > 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? > >

**References**:**Re: Simplify stuck in simple expression***From:*carlos@colorado.edu (Carlos Felippa)