Re: silly questions?

*To*: mathgroup at smc.vnet.net*Subject*: [mg59090] Re: [mg59052] silly questions?*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Thu, 28 Jul 2005 02:27:51 -0400 (EDT)*References*: <200507270526.BAA20063@smc.vnet.net> <43FD46F5-2F57-4927-B593-E6F118A539A0@mimuw.edu.pl>*Sender*: owner-wri-mathgroup at wolfram.com

On 27 Jul 2005, at 20:37, Andrzej Kozlowski wrote: > > > On 27 Jul 2005, at 07:26, Kent Holing wrote: > > >> Why does not (x^5-32)/(x-2)//FullSimplify in Mathematica work? >> Compare with Factor[x^5-32]//InputForm which returns (-2 + x)*(16 >> + 8*x + 4*x^2 + 2*x^3 + x^4). >> So why does not the first command just return 16 + 8*x + 4*x^2 + >> 2*x^3 + x^4? >> As in a factorization above, how is the easiest way to pick >> automatically (by a function) the factors of say degree >=2, if >> any ? >> >> Kent Holing >> >> >> > > Very "simple". What makes you think the cancelled out form is > "simpler"? > > > LeafCount[(x^5-32)/(x-2)] > > > 11 > > while > > > LeafCount[Cancel[(x^5-32)/(x-2)]] > > > 18 > > The cancelled form is much more "complicated", at least as measured > by LeafCount (and Mathematica's default complexity function). > > So if you want your answer it is better to make ask Mathematica to > make the expression more "complex": > > > Simplify[(x^5 - 32)/(x - 2), ComplexityFunction -> > (1/LeafCount[#1] & )] > > > x^4 + 2*x^3 + 4*x^2 + 8*x + 16 > > But it is of course much more sensible to just use Cancel. > > Andrzej Kozlowski > > > > Sorry, I forgot about your second question: Select[First[Transpose[FactorList[x^5 - 32]]], Exponent[#1, x] >= 2 & ] {x^4 + 2*x^3 + 4*x^2 + 8*x + 16} Andrzej Kozlowski

**References**:**silly questions?***From:*Kent Holing <KHO@statoil.com>