Factor and/or Rules replacements

*To*: mathgroup at smc.vnet.net*Subject*: [mg104443] Factor and/or Rules replacements*From*: yves <yves.dauphin at solvay.com>*Date*: Sun, 1 Nov 2009 03:56:16 -0500 (EST)

Hello everybody, Here is the model problem: I tried to obtain the factorisation of x^2+b x +c and expected to get something like (x-1/2(-b+Sqrt[b^2-4 c))((x-1/2(-b-Sqrt[b^2-4 c)). So I tried in:Factor[x^2+b x + c] and get out: c + b x + x^2 So my first question what should I have done? I tried another way in:sol=Solve[x^2+b x + c == 0,{x}]; and get the couple of replacement rules. Next I defined in: f=(x-x1)(x-x2) and finally I replaced x1 and x2 in succession by in:f /. {(sol[[1]] /. x -> x1), (sol[[2]] /. x -> x2)} which gave the expected factorisation but enclosed in {}. My second question is : Is there a simpler way or more compact to replace x1 and x2? With anticipated thanks. Yves

**Follow-Ups**:**Re: Factor and/or Rules replacements***From:*Adriano Pascoletti <adriano.pascoletti@dimi.uniud.it>

**Re: Factor and/or Rules replacements***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>