Re: Calculating derivate in Mathematica 9 giving wrong result
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- Subject: [mg131424] Re: Calculating derivate in Mathematica 9 giving wrong result
- From: "Nasser M. Abbasi" <nma at 12000.org>
- Date: Wed, 3 Jul 2013 22:03:42 -0400 (EDT)
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On 7/3/2013 3:52 AM, James wrote:
> In[5]:= D[(x^2 - 2)/(x^3 + 6), x]
>
> Out[5]= -((3 x^2 (-2 + x^2))/(6 + x^3)^2) + (2 x)/(6 + x^3)
>
> That is from Mathematica 9.
>
> The wolfram alpha site and my textbook give this answer:
>
> d/dx((x^2+x-2)/(x^3+6)) = (-x^4-2 x^3+6 x^2+12x+6)/(x^3+6)^2
>
> Please tell me what I am doing wrong.
>
but
D[(x^2 - 2)/(x^3 + 6), x]
is not the same as
d/dx( (x^2+x-2)/(x^3+6) )
you have an extra 'x' in the Alpha example.
--Nasser