Cancel[] and finite symbolic sums ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg102763] Cancel[] and finite symbolic sums ?*From*: Andre Holzner <andre.holzner at gmail.com>*Date*: Wed, 26 Aug 2009 07:44:51 -0400 (EDT)

Dear experts, I wonder what I'm doing wrong here... I try to simplify the following expression: [Sum[W * Subscript[b, k], {k, 1, N}]/W by doing Cancel[Sum[W * Subscript[b, k], {k, 1, N}]/W] it looks like Mathematica just returns me the original expression: Sum [W*Subscript[b, k], {k, 1, N}]/W When I try a sum over b instead of Subscript[b, k], it seems to work as expected: Cancel[Sum[W * b, {k, 1, N}]/W] gives: b*N Any ideas what I'm doing wrong ? thanks, Andre