Thank you Markus. It is always a nice thing to stay in contact.
In this case it was absolutely my foult, I can't eplain in rational way.
- I have no contact with math so many years
- There is a confusion in math descriptions in English and my mother tonge (Polish)
- I have written a question before I think enaugh (most probable)
Anyway, problem with Abs is solved and thank you again for your note. Who knows what will be if I will try more sophisticated operations ?)