Quantified Statements

Quantified Statements-ALL

Universal Quantifier : $\forall$, All

$e.g.\\ A=\{1, 2, 3, 4, 5\}\\ \ \forall\ x \in A, x>0$ : Universal Statement

counter example : 반례

Quantified Statements-THERE EXISTS

Existential Quantifier : $\exist$, there exists

Negations of Quantified Statements

$\forall$ → $\exist \neg$

$\exist$ → $\forall \neg$