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Re: Possible bug concerning a limit computation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71179] Re: [mg71107] Possible bug concerning a limit computation
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 9 Nov 2006 03:41:33 -0500 (EST)
  • Reply-to: hanlonr at cox.net

$Version

5.2 for Mac OS X (June 20, 2005)

expr=(Sqrt[7x^4+6x+5]-Sqrt[7x^4+3x+3])*
      Sqrt[63x^2-5x+20];

Limit[expr,x->Infinity]

9/2

Series[expr,{x,Infinity,0}]//Normal

9/2


Bob Hanlon

---- geo_topos <geo_topos at yahoo.co.uk> wrote: 
> Hello everyone,
> I don't know if this is the right place to post this, but here it goes.
> I am a high-school math teacher from greece. I was working with my
> students on the limit:
> 
> Limit[ (Sqrt[7x^4+6x+5] - Sqrt[7x^4+3x+3]) * Sqrt[63x^2-5x+20, x->
> Infinity]
> 
> The result we got for that is 9/2. Mathematica 4.0 will produce the
> opposite result: -9/2.
> If anyone is interested on the way we calculated this limit, please
> e-mail me and I will be more than happy to send you a copy of our
> computation, since it would take me ages to type this in ASCII and
> furthermore it would be, at least, annoying to the viewer.
> 
> Excuse my rusty english, best regards
> Kostas Raptis
> 


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