A Question about Expression Simplication

*To*: mathgroup at smc.vnet.net*Subject*: [mg31553] A Question about Expression Simplication*From*: "Lewis" <ylcsk at yahoo.com>*Date*: Sun, 11 Nov 2001 00:34:38 -0500 (EST)*Organization*: Hong Kong University of Science and Technology*Sender*: owner-wri-mathgroup at wolfram.com

Hi MathGroup, I am a beginner to Mathematica. Please help me solve the following problem. I am trying to manipulate expressions like: Sum[x_i, {i,1,T}] - x_2 or Sum[x_i, {i,1,T}] - Sum[x_i, {i,1,2,T}] I want to keep the upper limit as T, not any specific numeric value. I tried to use Simplify as in Simplify[Sum[x_i, {i,1,T}] - x_2] But the x_2 term doesn't get cancelled out. I also tried: Simplify[Sum[x_i, {i,1,T}] - x_2, T>2], but it didn't seem to work either. So I am wondering if the simplication only works when I specify the value for T. Any advice, please? Thank you very much! Best, Lewis.