运算及其性质 Proposition 3.1 Let Zn be the set of equivalence classes of the integers mod n and a,b,c∈Zn. 1.Addition and multiplication are commutative: 2.Addition and multiplication are associative: 3.There are both an additive and a multiplicative identity: 4.Multiplication distributes over addition: 5.For every integer a there is an additive inverse-a: 6.Let a be a nonzero integer.Then ged(a,n)=1 if and only if there erists a multiplicative inverse b for a (mod n);that is,a nonzero integer b such that ab≡1(modn.运算及其性质