Re: How can I force mathematica to collect a symbol from a polynomial

*To*: mathgroup at smc.vnet.net*Subject*: [mg130423] Re: How can I force mathematica to collect a symbol from a polynomial*From*: Peter Pein <petsie at dordos.net>*Date*: Wed, 10 Apr 2013 00:52:47 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net*References*: <kk0i2o$2te$1@smc.vnet.net>

Am 09.04.2013 10:04, schrieb syzhaoyu at gmail.com: > Let's say I have a polynomial: > a+b+c > Is there any way I can force mathematica to produce the following result: > a*(1+b/a+c/a) > > I think such transformation of polynomials should be very common; however, I have been trying all day and still can not get mathematica to do so automatically. > Try this: FactorOut[pol_, var_] := var*HoldForm@Expand[pol/var] // ReleaseHold FactorOut[a + b + c, a] --> a (1 + b/a + c/a) Collect[Expand[(a + b)^4 (x + y)^3 - (a - b)^4 (x - y)^3], x | y, FactorOut[#, a^Exponent[#, a]] &] --> a^3 (8 b + (8 b^3)/a^2) x^3 + a^4 (6 + (36 b^2)/a^2 + (6 b^4)/a^4) x^2 y + a^3 (24 b + (24 b^3)/a^2) x y^2 + a^4 (2 + (12 b^2)/a^2 + (2 b^4)/a^4) y^3 etc. Peter