Divisibility

There can be divisibility of Integers, as well as other sets of numbers. The notation is $a|b:a=b\times c⟺cϵz$.

Note that $b|a$ implies $b\le a$ in the positive integers, but not the full set of $z$. A formal proof would be as follows: prove at home

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$$b|a⟹\zeta cϵz:a=bc$$

$$a|b⟹\zeta dϵz:b=ac$$

$$\dots \text{continue later}$$