How to calculate the partial derivative?

*To*: mathgroup at smc.vnet.net*Subject*: [mg128726] How to calculate the partial derivative?*From*: Tang Laoya <tanglaoya1989 at gmail.com>*Date*: Wed, 21 Nov 2012 19:48:14 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Dear all, I am trying to calculate the partial derivative by mathematica, I have the following commands: L1=a1+b1*x+c1*y; L2=a2+b2*x+c2*y; L3=a3+b3*x+c3*y; NN=L1*L2; DNx=D[NN,x]; I got the following result: DNex=b2 (a1+b1 x+c1 y)+b1 (a2+b2 x+c2 y) How to do to have the following result? DNex=b2*L1 + b1 * L2 Thanks, Tang Laoya

**Follow-Ups**:**Re: How to calculate the partial derivative?***From:*Bob Hanlon <hanlonr357@gmail.com>

**Re: How to calculate the partial derivative?***From:*Bob Hanlon <hanlonr357@gmail.com>

**Re: How to calculate the partial derivative?***From:*Bob Hanlon <hanlonr357@gmail.com>