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Re: why is this happening?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99223] Re: why is this happening?
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Thu, 30 Apr 2009 06:22:50 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <gt9aq0$q7o$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,
and you are sure that you not mean

Solve[k2/k1 + ld^2 + ld == 0, ld]

vs

Solve[k1 ld + k2 + k1*ld^2 == 0, ld]

or do you just like to ask why Mathematica
return different answers for nonequivalent input ?

Regards
   Jens

sean_incali at yahoo.com wrote:
> Consider the following.
> 
> Solve[k1 ld + k1 k2 + ld^2 == 0, ld]
> 
> vs
> 
> Solve[k2/k1 + ld^2 + ld == 0, ld]
> 
> 
> I expected to get the output I got from the first code.
> 
>>From the second code, I was expecting something along the lines of
> 
> ld ->-1 + (SquareRoot[1 - 4 (k2/k21)])/2
> ld -> -1 - (SquareRoot[1 - 4 (k2/k21)])/2
> 
> since that is the answer.
> 
> Why is Mathematica turning the second scaled equation into the
> unscaled one in the first before solving it?
> 
> Thanks for any insight.
> 
> Sean
> 
> 


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