|   | 1 |  initial version  | 
Your example is a bit messy, but I suggest you to try combine() and denominator() functions:
http://www.sagemath.org/doc/reference/sage/symbolic/expression.html#sage.symbolic.expression.Expression.combine http://www.sagemath.org/doc/reference/sage/symbolic/expression.html#sage.symbolic.expression.Expression.denominator
 Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.
 
                
                Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.