4.2 指數(shù)函數(shù)

1、4.2 4.2 指數(shù)函數(shù)指數(shù)函數(shù)【復(fù)習(xí)目標】【復(fù)習(xí)目標】1.掌握指數(shù)函數(shù)的圖象與性質(zhì)掌握指數(shù)函數(shù)的圖象與性質(zhì).2.能利用指數(shù)函數(shù)性質(zhì)解決問題能利用指數(shù)函數(shù)性質(zhì)解決問題.【知識回顧】【知識回顧】1.函數(shù)函數(shù)y=ax(a0且且a1,xR)叫做指數(shù)函數(shù)叫做指數(shù)函數(shù).2.一般地一般地,指數(shù)函數(shù)指數(shù)函數(shù)y=ax(a0,a1)在其底數(shù)在其底數(shù)a1及及0aa1 10 0aay0 0;( ;(3 3) )函數(shù)的圖象都通過點函數(shù)的圖象都通過點( (0 0, ,1 1) )( (4 4) )在在( (-, ,+) )上是增函數(shù)上是增函數(shù); ; ( (4 4) )在在( (-, ,+) )上是減函數(shù)上是減函數(shù); ;

2、( (5 5) )當(dāng)當(dāng)xx0 0時時, ,yy1 1; ;當(dāng)當(dāng)xx0 0時時, ,0 0yyx0 0時時, ,0 0yy1 1; ;當(dāng)當(dāng)xxy1 1. .【例題精解例題精解】【例【例1】函數(shù)】函數(shù)y=5-x是是()A.增函數(shù)增函數(shù)B.減函數(shù)減函數(shù)C.奇函數(shù)奇函數(shù)D.偶函數(shù)偶函數(shù)【點評】請同學(xué)們根據(jù)指數(shù)函數(shù)的性質(zhì)分析解答這題【點評】請同學(xué)們根據(jù)指數(shù)函數(shù)的性質(zhì)分析解答這題.此題答案為此題答案為B.【點評】請同學(xué)們根據(jù)指數(shù)函數(shù)的性質(zhì)分析解答這題【點評】請同學(xué)們根據(jù)指數(shù)函數(shù)的性質(zhì)分析解答這題.【解】【解】(1)考查函數(shù)考查函數(shù)y=0.5x,它在實數(shù)集上為減函數(shù)它在實數(shù)集上為減函數(shù)30.53.1(2)考查函數(shù)考查函數(shù)y=3.14x,它在實數(shù)集上為增函數(shù)它在實數(shù)集上為增函數(shù)563.1450且且a1),以下說法中是不正確的是以下說法中是不正確的是()A.當(dāng)當(dāng)a1時是增函數(shù)時是增函數(shù)B.當(dāng)當(dāng)0aa0.7B.a0.8a0.7C.a21【答案答案】A【答案答案】C7.若指數(shù)函數(shù)若指數(shù)函數(shù)y=ax是減函數(shù)是減函數(shù),則下列不等式中則下列不等式中,成立的是成立的是()A.a1B.a1