Number Theory/Notation and Introduction to proof

Notation

$\mathbb {N} \,$ is the set of positive integers, also called the natural numbers.

$\mathbb {Z} \,$ is the set of all integers.

$\mathbb {Q} \,$ is the set of all rational numbers.

$\mathbb {A} \,$ is the set of algebraic numbers.

$\mathbb {R} \,$ is the set of real numbers.

$\mathbb {C} \,$ is the set of complex numbers.