Re: Simplify expression

*To*: mathgroup at smc.vnet.net*Subject*: [mg57815] Re: Simplify expression*From*: Bill Rowe <readnewsciv at earthlink.net>*Date*: Thu, 9 Jun 2005 05:17:51 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

On 6/8/05 at 3:21 AM, mbekkali at gmail.com (Mukhtar Bekkali) wrote: >I need to solve system of equations f1[x1,x2]=0,f2[x1,x2]==0, >however, some elements of these equation have the form >Sqrt[(x1^2-x2^2)^2]. It takes really long time to solve. If, >however, I manually simplify those elements, for example, >Sqrt[(x1^2-x2^2)^2]=x1^2-x2^2 then solve is fast. Therefore, the >question is how I can force mathematica simplify expressions of >this sort (another elements are fractions that depend on x1 and x2 >in Mathematica's mind but in reality they cancel out and fraction >becomes a number). I do not want to use FindRoot since I want to >see all solutions. Thanks, Mukhtar Bekkali I think PowerExpand is what you are looking for, i.e. PowerExpand[Sqrt[(x1^2-x2^2)^2]] yields x1^2 - x2^2 Solve doesn't use PowerExpand as one of the transforms to try since it will not yield valid results for all possible conditions. -- To reply via email subtract one hundred and four