1.整除,約數(shù),倍數(shù)概念.整數(shù)a除以整數(shù)b(b≠0)除得的商正好是整數(shù)而沒有余數(shù),我們就說a能被b整除,或b能整除a.a叫b的倍數(shù),b叫a的約數(shù)或因數(shù).約數(shù)和倍數(shù)相互依存,不能單獨(dú)說某個(gè)數(shù)是約數(shù)或倍數(shù).
18的約數(shù)有:1,2,3,6,9,18
2.質(zhì)因數(shù)：一個(gè)數(shù)的因數(shù)中,有質(zhì)數(shù)的因數(shù)叫這個(gè)數(shù)的質(zhì)因數(shù).
分解質(zhì)因數(shù)：把一個(gè)合數(shù)用質(zhì)因數(shù)相乘的形式表示出來.
18=2*3*3
18的質(zhì)因數(shù)有:2,3