群-一种“公理化”的代数系统 The law of composition is associative.That is, (aob)oc=ao(boc) fora,b,c∈G. There exists an element eE G,called the identity element,such that for any element a∈G eoa=aoe=a. For each element a e G,there exists an inverse element in G, denoted by a-1,such that aoa-1=a-loa=e. 注意：对于the integers mod n,加法一定构成群，乘法测未 必。群 – 一种“公理化”的代数系统 注意：对于theintegersmodn，加法一定构成群，乘法则未 必