Describe the predicate

Question

Let's describe the predicate p(x): "x belongs to A" in these cases:

1. $A=\{2n| n \in \Bbb N\}$
2. $A=\{2n+1| n \in \Bbb N\}$
3. $A=\{k^2| k \in \Bbb Z\}$

Answer 1

Hints:

1. $A=\{x\in \Bbb N\colon (\exists n\in \Bbb N)(x=2n)\}$
2. $A=\{x\in \Bbb N\colon (\exists n\in \Bbb N)(x=2n+1)\}$
3. $A=\{x\in \Bbb N\colon (\exists k\in \Bbb Z)(x=k^2)\}$