Division
If a and b are integers with a?0, we say that a divides b, if there is
an integer c such that b=ac, i.e. if b/a is an integer.
We write a|b to express that a divides b, and a†b to express that a
When a|b, we say that a is a factor of b and b is a multiple of a.
Examples: 3 12, 4 18, 1 1999, 1999 1999, 17 0, 0 17
Theorem 1. Let a, b and c be integers. Then:
1. if a|b and a|c, then a|(b+c);
3. if a|b and b|c, then a|c.