Re: "Solve" on polynomial equality results in expressions containing "Root"

*To*: mathgroup at smc.vnet.net*Subject*: [mg128523] Re: "Solve" on polynomial equality results in expressions containing "Root"*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Sun, 28 Oct 2012 01:55:40 -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

On 10/26/12 at 11:48 PM, coder0xff at gmail.com wrote: >If I do Solve[y==3x^2-2x^3,x] I get expressions containing imaginary >parts. If I set the domain to the Reals >(Solve[y==3x^2-2x^3,x,Reals]) then I got stuff like Root[y - 3 #1^2 >+ 2 #1^3 &, 2]. I know there's a solution using only reals (since >the range and domain are both real, and complex math is performed as >operations on reals after all) How can I get it to give me the >actual solution using only reals? Probably the simplest way to accomplish your goal is to let Solve return all solutions and delete the complex solutions, i.e., Cases[Solve[y == 3 x^2 - 2 x^3, x], _?(FreeQ[#, Complex] &)]