Simple Sum does not simplify

*To*: mathgroup at smc.vnet.net*Subject*: [mg55472] Simple Sum does not simplify*From*: ali_tofigh at hotmail.com (Alix)*Date*: Fri, 25 Mar 2005 05:48:14 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Here is a simple symbolic sum: Sum[n a[i] - Sum[a[j], {j, n}], {i, n}] This should simplify to 0, but it doesn't. Why and is there a way to get mathematica to work with these kind of sums? I'm using mathematica 5.0.