Number Theory-Divisibility

Definition 2.1 Divisibility
We say that a divides b, and we write a|b if b = ka for some k.
For example, 3|12, since 12 = 4 * 3, also 8|40, since 40 = 5 * 8. If a|b, we might also say "a is a divisor of b", "a is a factor of b", or " "b is a multiple of a". If a does not divide b, then we write a |/ b. For example, 3 |/ 14; also, 8 |/ 42.