Hi

I am a new member. As per my understanding, if a variable in a formula does not fall under a quantifer, it is free and if it does, it is bound.

Could you tell me if my understanding correct?

I am currently reading the book "mathmatical logic for computer science" page 106. Please see the attached image or visit

Mathematical logic for computer science - Google Books

a proof has been given which mentions

A'= x A1(x)

and then the text: but x is the only free variable in A1 ...........

My question is: is x free? It falls under for all quantifier ...

Sorry for the long question and thank you for your help.

Suzzane.