Unexpected behavior of Simplify

*To*: mathgroup at smc.vnet.net*Subject*: [mg63229] Unexpected behavior of Simplify*From*: gleam at flashmail.com*Date*: Tue, 20 Dec 2005 04:19:26 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hello MathGroup. What is the explanation for this behavior? In[1]:= \!\(ClearAll[a, b, c]\[IndentingNewLine] \(expr = c\^4\ b\^2 + a\^4\ b\^2 + c\^2\ a\^2\ \((1 - 2\ b\^2)\);\)\ \[IndentingNewLine] Simplify[expr]\[IndentingNewLine] Simplify[expr /. {a -> b, b -> a}] /. {a -> b, b -> a}\) Out[3]= \!\(a\^4\ b\^2 + a\^2\ \((1 - 2\ b\^2)\)\ c\^2 + b\^2\ c\^4\) Out[4]= \!\(a\^2\ c\^2 + b\^2\ \((a\^2 - c\^2)\)\^2\) The second application of the replacement is merely for clarity; the unexpected behavior is present without it. Paul