Subfield

Definition

• With $\mathbb{F}$ as a field, $K\subset \mathbb{F}$
• $K$ is a subfield if:
  1. $K$ contains atleast 2 elements
  2. $\forall a,b\in K,a+(-b)\in \mathbb{F}$
  3. $\forall a,b\in K,(b\ne 0),a{b}^1\in \mathbb{F}$