2020版高考數(shù)學(xué)復(fù)習(xí)第二單元第9講對數(shù)與對數(shù)函數(shù)練習(xí)文（含解析）新人教A版.docx

第9講對數(shù)與對數(shù)函數(shù)1.函數(shù)y=loga(3x-2)(a0且a1)的圖像經(jīng)過定點(diǎn)A,則點(diǎn)A的坐標(biāo)是()A.0,23B.23,0C.(1,0)D.(0,1)2.設(shè)a=log123,b=130,3,c=ln,則a,b,c的大小關(guān)系為()A.abcB.acbC.cabD.bac3.2018菏澤一模 若log12mlog12n,則下列不等式一定成立的是()A.14m1nC.ln(m-n)0D.3m-n0,2x,x0,則ff12的值是()A.2B.-2C.22D.-227.2018福州模擬 已知函數(shù)f(x)=log2x+a,x0,4x-2-1,x0,若f(a)=3,則f(a-2)=()A.-1516B.3C.-6364或3D.-1516或38.已知為銳角,且logasinlogbsin0,則a和b的大小關(guān)系為()A.ab1B.ba1C.0ab1D.0ba19.已知函數(shù)y=log13x的定義域?yàn)閍,b,值域?yàn)?,1,則b-a的取值范圍為()A.(0,3B.13,3C.0,83D.23,8310.已知x1=log132,x2=2-12,13x3=log3x3,則()A.x1x2x3B.x1x3x2C.x2x1x3D.x3x10,y0,x+y2=2,則log2x+2log2y的最大值為.13.若對于任意的實(shí)數(shù)x0,12,都有2-2x-logax0)與函數(shù)y=|log2x|的圖像交于A(x1,y1),B(x2,y2)(x1x2)兩點(diǎn),則下列說法中正確的是.(填序號)0x11x2;x1x2=1;2x1+2x24.15.如果一個(gè)點(diǎn)是一個(gè)指數(shù)函數(shù)和一個(gè)對數(shù)函數(shù)的圖像的交點(diǎn),那么稱這個(gè)點(diǎn)為“好點(diǎn)”.下列四個(gè)點(diǎn)P1(1,1),P2(1,2),P312,12,P4(2,2)中,“好點(diǎn)”的個(gè)數(shù)為()A.1B.2C.3D.416.已知直線l與函數(shù)f(x)=ln(ex)-ln(1-x)的圖像交于P,Q兩點(diǎn).若點(diǎn)M12,m是線段PQ的中點(diǎn),則實(shí)數(shù)m的值為()A.2B.1C.12D.14課時(shí)作業(yè)(九)1.C解析 當(dāng)3x-2=1,即x=1時(shí),y=loga1=0,故定點(diǎn)A的坐標(biāo)是(1,0).2.A解析a=log123log121=0,0130.3130=1,即0blne=1,abc.3.A解析 因?yàn)閘og12mn0,由冪函數(shù)的性質(zhì)得14n13n,由指數(shù)函數(shù)的性質(zhì)得14m14n,因此14m0,則f(a)=log2a+a=3,解得a=2,f(a-2)=f(0)=4-2-1=-1516;若a0,則f(a)=4a-2-1=3,解得a=3,不合題意舍去.所以f(a-2)=-1516,故選A.8.D解析0sinlogbsin0,0a1,0blogbsin,1logsina-1logsinb=logsinb-logsinalogsinalogsinb0,可得logsinblogsina,0sinb,故0ba1,而x1=log1320,0x2=2-12x2x1.故選A.11.A解析對于任意x10,2,存在x20,2,使得f(x1)g(x2),在0,2上,f(x)ming(x)min.f(x)=ln(x2+1)在0,2上單調(diào)遞增,f(x)min=f(0)=0.g(x)=12x-m在0,2上單調(diào)遞減,g(x)min=g(2)=122-m=14-m.由14-m0,得m14,實(shí)數(shù)m的取值范圍是14,+.故選A.12.0解析x0,y0,x+y2=2,xy2x+y222=1,當(dāng)且僅當(dāng)x=y2=1時(shí),等號成立,log2x+2log2y=log2x+log2y2=log2(xy2)log21=0.13.14a1解析 若對于任意的實(shí)數(shù)x0,12,都有2-2x-logax2-2x恒成立,即對任意的實(shí)數(shù)x0,12,y=logax的圖像恒在y=14x的圖像的上方,0a1,1212,a14.綜上可得,14a1.14.解析 作出函數(shù)y=|log2x|的圖像,如圖所示,該函數(shù)先減后增,且在x=1處取得最小值0.在同一平面直角坐標(biāo)系中作出直線y=m,兩圖像交于A,B兩點(diǎn),由圖可知,0x111-x1,x1+x22,2x1+2x222x1+x2222=4.綜上可得,中說法正確,中說法正確,中說法錯(cuò)誤,中說法正確.15.B解析 設(shè)指數(shù)函數(shù)和對數(shù)函數(shù)分別為y=ax(a0,a1),y=logbx(b0,b1).若P1為“好點(diǎn)”,則P1(1,1)在y=ax的圖像上,得a=1,與a0且a1矛盾;P2(1,2)顯然不在y=logbx的圖像上;P312,12在y=ax,y=logbx的圖像上時(shí),a=14,b=14;易得P4(2,2)是“好點(diǎn)”.故選B.16.C解析f(x)=ln(ex)-ln(1-x)=12+lnx1-x,設(shè)P(x1,f(x1),Q(x2,f(x2),則f(x1)=12+lnx11-x1,f(x2)=12+lnx21-x2,依題意