Thread: Divisibilty proofs?

Mathematical signs

Originally Posted by thegarden

Proofs required for the following divisibility rules:

1. a|1 implies a= plus or minus 1
2. a|b and b|a IF AND ONLY IF (IFF) a= plus or minus b
3. a|b IFF -a|b IFF a|(-b) IFF (-a)(-b)
4. Let b>0. If a|b implies a is less than or equal to b

Sorry for not inserting mathematical signs, new to the forum so just finding my way around, many thanks.

Use definition of division. I do the first one. .

And second one , .
Thus, (assuming ).