Newbie Question: How to simplify expression

*To*: mathgroup at smc.vnet.net*Subject*: [mg66834] Newbie Question: How to simplify expression*From*: "duli" <dulipishi at gmail.com>*Date*: Thu, 1 Jun 2006 06:54:26 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Hello: If I have an expression of the form (-1)^(2 x y + z) + (-1)^x where x,y, z are integers, I want Mathematica to simplify this to (-1)^z + (-1)^x How do I do this ? Thanks! Duli