Question

函數(shù)y=a^x與y=log_a

1

x

（a＞0，且a≠1）在同一平面直角坐標(biāo)系中的圖象的形狀可能是（　�。�

• A、
• B、
• C、
• D、

Answer 1

考點(diǎn)：函數(shù)的圖象

專題：函數(shù)的性質(zhì)及應(yīng)用

分析：分別確定指數(shù)函數(shù)的底數(shù)a和對(duì)數(shù)函數(shù)的底數(shù)a是否對(duì)應(yīng)即可．

解答： 解：對(duì)于A．指數(shù)函數(shù)的底數(shù)a＞1，則對(duì)數(shù)函數(shù)的定義域錯(cuò)誤，所以A不可能．
對(duì)于B．指數(shù)函數(shù)的底數(shù)a＞1，則對(duì)數(shù)函數(shù)單調(diào)性遞減，圖象是對(duì)應(yīng)的，所以B有可能．
對(duì)于C．指數(shù)函數(shù)的底數(shù)a＞1，此時(shí)對(duì)數(shù)函數(shù)應(yīng)為減函數(shù)，所以C不可能．
對(duì)于D．指數(shù)函數(shù)的底數(shù)a＜1，此時(shí)對(duì)數(shù)函數(shù)應(yīng)為增函數(shù)，所以D不可能．
故選B．

點(diǎn)評(píng)：本題主要考查函數(shù)圖象的識(shí)別，主要是利用指數(shù)函數(shù)和對(duì)數(shù)函數(shù)的圖象性質(zhì)來判斷．