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1、素材庫素材庫1.1.對數(shù)函數(shù)的圖象與性質(zhì)對數(shù)函數(shù)的圖象與性質(zhì)底數(shù)底數(shù)圖圖象象定義域定義域值域值域性質(zhì)性質(zhì)a1a10a10a1R R(0,+(0,+) )(1)(1)過定點過定點(1(1,0)0),即,即x=1x=1時,時,y=0y=0(3)(3)當當0 x10 x1時,時,y0;y1x1時,時,y0.y0.(3)(3)當當x1x1時,時,y0.y0.當當0 x10 x0.y0.(2)(2)在在(0,+(0,+) )上是增函數(shù)上是增函數(shù)(2)(2)在在(0,+(0,+) )上是減函數(shù)上是減函數(shù)2.2.指數(shù)函數(shù)與對數(shù)函數(shù)的聯(lián)系與區(qū)別指數(shù)函數(shù)與對數(shù)函數(shù)的聯(lián)系與區(qū)別指數(shù)函數(shù)指數(shù)函數(shù)y=ay=ax x(
2、 (a a0,a1)0,a1)對數(shù)函數(shù)對數(shù)函數(shù)y=logy=loga ax(ax(a0,a1)0,a1)定義域定義域值域值域圖象圖象xRxR x(0,+)x(0,+)yy(0 0,+)yRyR指數(shù)函數(shù)指數(shù)函數(shù)y=ay=ax x( (a a0,a1)0,a1)對數(shù)函數(shù)對數(shù)函數(shù)y=logy=loga ax(ax(a0,a1)0,a1)性質(zhì)性質(zhì)過定點(過定點(0 0,1 1)過定過定點點(1 1,0 0)減函數(shù)減函數(shù)增函數(shù)增函數(shù)減函數(shù)減函數(shù)增函數(shù)增函數(shù)x(-x(-,0)0)時,時,y(1,+)y(1,+)x(0,+)x(0,+)時,時,y(0,1)y(0,1)x(-,0)x(-,0)時時,y(0,1
3、) ,y(0,1) x(0,+)x(0,+)時時,y(1,+),y(1,+)x(0,1)x(0,1)時,時,y(0,+) y(0,+) x(1,+)x(1,+)時時,y(-,0),y(-,0)x(0,1)x(0,1)時,時,y=(-,0) y=(-,0) x(1,+)x(1,+)時,時,y(0,+)y(0,+)0 0a ab b1 1 0 0 1 1111 1 1.1.對數(shù)函數(shù)圖象對數(shù)函數(shù)圖象1 11 1x xy yOy=logy=log2 2x xy=lgxy=lgx110ylog x12ylog xx=1x=12.2.指數(shù)函數(shù)與對數(shù)函數(shù)指數(shù)函數(shù)與對數(shù)函數(shù)x xOy yy=xy=xy=2y=
4、2x xy=logy=log2 2x xx1y( )212ylog x1 1對數(shù)式對數(shù)式x xlogloga aN N中,中,a a的取值范圍是的取值范圍是_,N N的取值范圍是的取值范圍是_. .2 2logloga a1(1(a a00,且,且a a1)1)_._.3 3一般地,我們把函數(shù)一般地,我們把函數(shù)y ya ax x( (a a00且且a a1)1)叫做叫做_函數(shù),它的定義域為函數(shù),它的定義域為R R,值域為,值域為_,把指數(shù)式把指數(shù)式y(tǒng) ya ax x化為對數(shù)式為化為對數(shù)式為x xlogloga ay y. .aa0 0且且a a11N N 000 0(0(0,) )指數(shù)指數(shù)logaxx (0,)對數(shù)函數(shù)的定義對數(shù)函數(shù)的定義一般地,我們把函數(shù)y_(a0,且a1)叫做對數(shù)函數(shù),其中_是自變量,函數(shù)的定義域是_歸納總結(jié)(1)由于指數(shù)函數(shù)yax中的底數(shù)a滿足a0,且a1,則對數(shù)函數(shù)ylogax中的底數(shù)a也必須滿足a0,且a1.(2)對數(shù)函數(shù)的解析式同時滿足:對數(shù)符號前面的系數(shù)是1;對數(shù)的底數(shù)是不等于1的正實數(shù)(常數(shù));對數(shù)的真數(shù)僅有自變量x.a0,且,且a1N0011指數(shù)指數(shù) (0,)答案:答案:(2,5