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Re: Calculating derivate in Mathematica 9 giving wrong result

• To: mathgroup at smc.vnet.net
• Subject: [mg131422] Re: Calculating derivate in Mathematica 9 giving wrong result
• From: Bob Hanlon <hanlonr357 at gmail.com>
• Date: Wed, 3 Jul 2013 22:03:02 -0400 (EDT)
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• References: <20130703090146.A8EAD6AD9@smc.vnet.net>

You used different functions



D[(x^2 - 2)/(x^3 + 6), x] // Simplify // TraditionalForm


(x*(12 + 6*x - x^3))/(6 + x^3)^2



D[(x^2 + x - 2)/(x^3 + 6), x] // Simplify // TraditionalForm


(-x^4 - 2*x^3 + 6*x^2 +
      12*x + 6)/(x^3 + 6)^2



Bob Hanlon


On Wed, Jul 3, 2013 at 5:01 AM, James <jhlawley at gmail.com> 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.
>
>

• References:
  • Calculating derivate in Mathematica 9 giving wrong result
    • From: James <jhlawley@gmail.com>