Re: Form of a linear equation

*To*: mathgroup at smc.vnet.net*Subject*: [mg53747] Re: [mg53734] Form of a linear equation*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Wed, 26 Jan 2005 04:36:26 -0500 (EST)*References*: <200501251003.FAA14449@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

On 25 Jan 2005, at 10:03, DJ Craig wrote: > I'm trying to convert this linear equation: > > -(4+4x+y) / 17^(1/2) = (2+x+y) / 2^(1/2) > > into the form: > > (a_)*x + (b_)*y + (c_) = 0 > > This sounds simple enough, but I can't figure out how to make > Mathematica do it. My TI-89 does it automatically, but I need to be > able to do this like a batch process for a bunch of linear equations. > Heres the solution the TI-89 gives me: > > \!\(\* > StyleBox[\(\((\(\(-4\)\ \@17\)\/17 - \@2\/2)\)\ x + \((\(-\@17\)\/17 > - \ > \@2\/2)\)\ y - \(3\ \@17\)\/17 - \@2 = 0\), > FontWeight->"Bold"]\) > > Just copy and paste that mess into Mathematica and it will change into > the equation at the top, but in the form that I want it. > > I haven't been using Mathematica for long. I'm used to my TI-89; I've > been using it for years. One way is to use Collect: eq=-(4+4x+y) / 17^(1/2) == (2+x+y) / 2^(1/2); Collect[eq /. Equal -> Subtract, {x, y}] == 0 (-(1/Sqrt[2]) - 4/Sqrt[17])*x + (-(1/Sqrt[2]) - 1/Sqrt[17])*y - 4/Sqrt[17] - Sqrt[2] == 0 If you have several equations you can use Map: (Collect[#1 /. Equal -> Subtract, {x, y}] == 0 & ) /@ {2*x + 3*y == x - y, 5*x - y == x + 2*y} {x + 4*y == 0, 4*x - 3*y == 0} Andrzej Kozlowski Chiba, Japan http://www.akikoz.net/~andrzej/ http://www.mimuw.edu.pl/~akoz/

**References**:**Form of a linear equation***From:*"DJ Craig" <spit@djtricities.com>