Hi, I've just started using GiNaC (and very nice it is too!), however I have some strange behavior with an expression not being simplified. One output of a linear equation solver is the expression: (C_2 *s ^ 2 *L_2 *V_1 + C_2 *L_1 *C_1 *s ^ 4 *L_2 *V_1 + L_1 *C_1 *s ^ 2 *V_1 + V_1 )*(1 +L_1*C_1*s^2+C_2*L_1*s^2+C_2*L_1*C_1*s^4*L_2+C_2*s^2*L_2)^(-1)*V_1^(-1) What is happening is that the V_1 terms in the first bracket are not being factorised, and therefore no cancellation with the final (V_1)^(-1) term is occuring. All my symbols are created with a SymbolFactory pattern, so I can be sure each V_1 is the same object. Can anyone suggest why GiNaC isn't simplifying this to cancel the V_1 terms? Regards, James.