IDEA: clear a-z cmd

[Arno K]

Is √(y^2*z+5*y*z+4)+2)/y different from √(598)+2)/6) with y=6 and z=9? No, so the result is correct.
So one has to be aware of the variables one has used before and then gets the desired symbolic results. I myself usually nearly never assign values to variables used in cas and have some rules I follow when I do so. Nevertheless the idea of spending purge some more parameters is not bad.
Arno