Trivial changes to formula

*To*: mathgroup at smc.vnet.net*Subject*: [mg32533] Trivial changes to formula*From*: stevebg at adelphia.net (Steve Gray)*Date*: Sat, 26 Jan 2002 04:07:50 -0500 (EST)*Organization*: The Math Forum*Sender*: owner-wri-mathgroup at wolfram.com

I have a large series of expressions like this: ((-z0+za)(-z0+zb)(-z0+zc))/((-z0+z1)(-z0+z2)(-zo+z3)) where it is important, for recognizing a pattern that may or may not run through the entire formula, to change the order of some of the terms to (za-z0) (no sign change) or (z0-z1) (has a sign change), etc. I need to tell it conveniently which terms to reverse, and I want it to automatically change the sign of the whole expression if necessary to keep the value correct. Is there a way to do this?