read about ratsubst. RJF Albert Reiner wrote: > [edA-qa mort-ora-y <eda-qa@disemia.com>, Thu, 23 Sep 2004 14:28:51 +0200]: > >>I want to achieve the following: >> >> Given: (x+y+z)*c >> Simplify Where: a=x+y >> Result: (a+z)*c > > > subst(a-x, y, (x+y+z)*c) ==> c*(z+a) >