【導(dǎo)讀】①理解對(duì)數(shù)的概念及其運(yùn)算性質(zhì);自然對(duì)數(shù)或常用對(duì)數(shù);了解對(duì)數(shù)在簡(jiǎn)化運(yùn)算中的作用.③體會(huì)對(duì)數(shù)函數(shù)是一類重要的函數(shù)模型;①零和負(fù)數(shù)沒有對(duì)數(shù),即N>0;③底的對(duì)數(shù)等于1,即;叫做對(duì)數(shù)函數(shù),其中x是自變量.的都不是對(duì)數(shù)函數(shù).求能使y為負(fù)值的x的取值范圍.[a,2a]上的最大值是最小值的3倍,則a=.函數(shù)的圖象,已知a取,,2,3,