Re: Radicals simplify

*To*: mathgroup at smc.vnet.net*Subject*: [mg106372] Re: [mg106361] Radicals simplify*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Mon, 11 Jan 2010 05:27:53 -0500 (EST)*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst*References*: <201001100830.DAA05621@smc.vnet.net>*Reply-to*: murray at math.umass.edu

But (x^6 y^3)^(1/4) *is* the correct answer, since from one viewpoint it is simpler than the answer x(x^2 y^3)^(1/4) that you prefer. The issue is the simplicity of the structure of the answer. Evaluate the Depth, or even the TreeForm, of both answers, and you'll see that the answer Mathematica gave you is in fact "simpler" in that it has a depth of 4, whereas the one you prefer has a depth of 5. When evaluating a Simplify, by default Mathematica uses a ComplexityFunction that counts the subexpressions and digits of integers. (But the documentation seems mute as to exactly how Mathematica weighs those two things: just the sum of the two, or what?) On 1/10/2010 3:30 AM, francix wrote: > Hi, > I am using Matematica 7 and need some help with Radicals. > > If I do > Simplify[(x^4 y^3)^(1/4), x>= 0] I correctly have > > x (y^3)^(1/4) > > But If I do > > Simplify[(x^6 y^3)^(1/4), x>= 0] I get > > (x^6 y^3)^(1/4) and not the correct answer x(x^2 y^3)^(1/4) > > Thanks in advanced. > > > > > > > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305

**References**:**Radicals simplify***From:*"francix" <fracix@gmail.com>