Re: Calculating derivate in Mathematica 9 giving wrong result

*To*: mathgroup at smc.vnet.net*Subject*: [mg131418] Re: Calculating derivate in Mathematica 9 giving wrong result*From*: Frank K <fkampas at gmail.com>*Date*: Wed, 3 Jul 2013 22:01:42 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net*References*: <kr0oo9$3eu$1@smc.vnet.net>

On Wednesday, July 3, 2013 4:52:25 AM UTC-4, 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. Your input to Mathematica is not the same as your input to Wolfram Alpha. x*x -2 is the numerator for your input to Mathematica. Your input to Wolfram Alpha is x*x +x -2