Why relation divisibility is not relation partially ordered set on set Integer? I try get it why relation divisibility is not relation partially ordered set.
$A=\{−2, 2, 4, 6, 8, 10\}$
with relation divisibility "|" 
$R$ is relation divisibility | when $a,b,c \in Z : a = b \cdot c$
For relation partially ordered set must be relation:


*

*reflexive (fulfil) - everery number could have divisible with yourself

*antisymmetric (fulfil) - smaller number could have divisible with bigger, but not the otherway

*transitive (not fulfil) - why please? 

Divisibility is not antisymmetric on your $A$ because $-2\mid 2$ and $2\mid{-2}$.
