351對(duì)數(shù)函數(shù)(1)[1]

1、細(xì)胞分裂問題：細(xì)胞分裂問題：細(xì)胞的個(gè)數(shù)是分裂次數(shù)的指數(shù)函數(shù)細(xì)胞的個(gè)數(shù)是分裂次數(shù)的指數(shù)函數(shù) .反反之，細(xì)胞分裂的次數(shù)是細(xì)胞個(gè)數(shù)的函數(shù)之，細(xì)胞分裂的次數(shù)是細(xì)胞個(gè)數(shù)的函數(shù) 由對(duì)數(shù)定義：由對(duì)數(shù)定義： 即：次數(shù)即：次數(shù)y是個(gè)數(shù)是個(gè)數(shù)x的的函數(shù)函數(shù) .定義：函數(shù)定義：函數(shù) 叫做對(duì)數(shù)函數(shù)；叫做對(duì)數(shù)函數(shù)；它是指數(shù)函數(shù)它是指數(shù)函數(shù) 的反函數(shù)。的反函數(shù)。 對(duì)數(shù)函數(shù)對(duì)數(shù)函數(shù) 的定義域?yàn)榈亩x域?yàn)?，值域，值域?yàn)闉?。xy2yx2logxy2logxyalogxay ) 10(aa且), 0( ),(xyalog溫故知新先看先看y=2x 與與y=log2x指數(shù)函數(shù)、對(duì)數(shù)指數(shù)函數(shù)、對(duì)數(shù)函數(shù)的圖像有何函數(shù)的圖像有何關(guān)系呢

2、？關(guān)系呢？y=2x 圖像的關(guān)系y=2xy=xy=2xy=xy=log2xy=2x對(duì)數(shù)函數(shù)解析式y(tǒng)=logax (a0,a1)指數(shù)函數(shù)與對(duì)數(shù)函數(shù)指數(shù)函數(shù)與對(duì)數(shù)函數(shù)圖象間的關(guān)系指數(shù)函數(shù)與對(duì)數(shù)函數(shù)指數(shù)函數(shù)與對(duì)數(shù)函數(shù)圖像間的關(guān)系 a1 0a1 0a1 0 x1 y0y = 0 y0 y0,a1,x0)(1) y= +1例題例題2. 求下列函數(shù)的定義域：求下列函數(shù)的定義域： (1) y=logax2 (0a1) (2) y=log3(9x2) (3) y= 怎樣求上述函數(shù)的值域怎樣求上述函數(shù)的值域？3log x小小 結(jié)結(jié)求函數(shù)定義域的方法求函數(shù)定義域的方法:1. 分?jǐn)?shù)的分母不能為零分?jǐn)?shù)的分母不能為零;3. 偶次方根的被開方數(shù)大于偶次方根的被開方數(shù)大于等于零等于零;4. 對(duì)數(shù)的真數(shù)必須大于零對(duì)數(shù)的真數(shù)必須大于零;5. 指數(shù)指數(shù),對(duì)數(shù)的底數(shù)必須大對(duì)數(shù)的底數(shù)必須大于零且不等于于零且不等于1.2. 零的指數(shù)不能為零和負(fù)數(shù)零的指數(shù)不能為零和負(fù)數(shù);課堂小結(jié)課堂小結(jié)1. 對(duì)數(shù)函數(shù)的定義、圖象對(duì)數(shù)函數(shù)的定義、圖象2. 對(duì)數(shù)函數(shù)與指數(shù)函數(shù)的對(duì)數(shù)函數(shù)與