数论

因数，倍数，余数，不完全商

b | a, c | b => c | a

a | m. b | m => (a + b) | m

a | m, q∈Z => aq | m

公因数，最大公因数，互质（素），两两互质

两两互质 => 互质 <=> 最大公因数为1

(a, b) = (|a|, |b|)

(0, b) = |b|

(a, b) = (b, a mod b)

辗转相除法

(a, b) = (b, r1) = (r1, r2) = ... = (rn, 0) = |rn|, r1 ≡ a mod b, ……

(am, bm) = (a, b)m

(a, b) = c, (c, d) = e => (a, b, c) = e

最小公倍数

a * b = (a, b) * [a, b]