Pilou,

>> Does exist a trick for see if the are Macros or not ? <<

Yes, the macros are darker, but there are no macros used in example above.

>> And i see (1-a)*b how do you enter (1-a) ? <<

As well as preset functions, you can type custom functions into Math node's F field.
See image below

>> Cool <<

Cheers
James
https://www.instagram.com/nodeology/