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Re: Matrix Form of Quadratic Equations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114254] Re: Matrix Form of Quadratic Equations
  • From: Fred Simons <f.h.simons at tue.nl>
  • Date: Mon, 29 Nov 2010 06:06:11 -0500 (EST)

Op 28-11-2010 12:54, Simon schreef:
> On Nov 26, 6:32 pm, Ari<ari... at finly.net>  wrote:
>> Hello,
>>
>> Could anyone guide me how to build a mathematica module to form a Matrix 
> form from a quadratic equations?
>> For example, x^2 + y^2 - 2 x y will output
>> {{1, -1}, {-1, 1}} ?
>>
>> Thanks
> Hi there,
>
> I was sure that you would be inundated with answers...
(....)

Yes, that was my feeling too. The good old SolveAlways (unchanged since 
version 1) seems to be forgotten:

In[198]:= SolveAlways[{x,y}. {{a,b},{b,c}}. {x,y}== x^2 + y^2 - 2 x y, 
{x,y}]

Out[198]= {{a->1,b->-1,c->1}}

Fred Simons
Eindhoven University of Technology


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