Need help on simplifying formula

• To: mathgroup at smc.vnet.net
• Subject: [mg6769] Need help on simplifying formula
• From: j-levy at nwu.edu (Joseph Levy)
• Date: Wed, 16 Apr 1997 02:15:04 -0400 (EDT)
• Organization: Northwestern University
• Sender: owner-wri-mathgroup at wolfram.com

```Hello

I hope that anyone can help me with this:

I defined pij,

In[1]:= pij=ai bj Exp[tj(1-ti)]

(1 - ti) tj
Out[1]= ai bj E

and then I computed the derivative of pij by tj, and I got the correct answer
(off course):

In[2]:= D[pij,tj]

(1 - ti) tj
Out[2]= ai bj E            (1 - ti)

But when looking carefully, D[pij,tj]==pij (1-ti).

How do I get Mathematica to get this? I tried to work with commands like Rules
and replace.

Any help will be apriciated.

Joseph ("Yossi") Levy     Phone : (847) 467-4095
Department of Marketing   Fax   : (847) 491-2498
Kellogg Graduate School   E-mail: j-levy at nwu.edu
Northwestern University

```

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