【導(dǎo)讀】求原函數(shù)的值域,例1:求下列函數(shù)的反函數(shù)。對(duì)數(shù)的真數(shù)必須大于0;指數(shù)函數(shù)、對(duì)數(shù)函數(shù)的底數(shù)要滿足大于0且不等于1;實(shí)際問題要有意義.①底數(shù)相同時(shí)考慮對(duì)數(shù)函數(shù)的單調(diào)性;②底數(shù)不同時(shí)要借助于中間量。對(duì)數(shù)函數(shù)與指數(shù)函數(shù)的圖象關(guān)于直線y=x對(duì)稱。