Re: How to "Factorize" expanded derivatives

• To: mathgroup at smc.vnet.net
• Subject: [mg17178] Re: How to "Factorize" expanded derivatives
• From: jf alcover <jfalcover at cepme.fr>
• Date: Tue, 20 Apr 1999 01:20:54 -0400
• Organization: cepme
• References: <7f9evt\$50m@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hemming,
this is what i propose, (but i dont know if its really
what you are looking for ! ) :

In[1]:=HoldIntegrate[expr_,x_]:=
Module[{integ,h1,h2},
integ=Integrate[expr,x];
h1[h2[integ,x]]/.h1->Hold/.h2->D
];

In[2]:=HoldIntegrate[g[x]f'[x]+f[x]g'[x],x]//InputForm
Out[2]:=Hold[D[f[x]*g[x], x]]

In[3]:=(%//Release)==g[x]f'[x]+f[x]g'[x]
Out[3]:=True

Regards

"Hemming A Schaeffer" wrote:

> Consider the operation
>
> D[f[x]g[x],x]=g[x]f'[x]+f[x]g'[x]
>
> Does anyone know how to make Mathematica perform the inverse operation.
I
> guess what I am looking for is some kind of Simplify Function using
> differentiation rules. Something resembling the Factor Function would also
> be nice.
>
> Thanks for any tips
>
> Hemming

```

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