loga,logb,logc成等比数列,且a b c=4

解析,00>log(a)blog(a)blog(b)(1/b)>log(a)

可以,但要注意A,B都要大于0,另外,你没写底数,一般以10为底写为lg,不是log再问：这个倒是知道，就记不太清可不可以倒过来用了，谢谢提醒哦~再答：不客气，从左到右A,B都负可写为lg(A*B)=

N设y＝logay则a＝N．两边取以a为底的对数aNylogm＝logmNlogmy＝－－－－－alogmNNlogm即loga＝－－－－－－a．logm设a^b=N…………①则b=logaN…………

a>b>1,loga(b)>1logb(a)

loga(c),logb(c)是方程x^2-3x+1=0的两根loga(c)+logb(c)=3loga(c)*logb(c)=1logc(a)+logc(b)=1/loga(c)+1/logb(c)

由题意可知loga(c)+logb(c)=3loga(c)logb(c)=1,即1/logc(a)+1/logc（b）=3,即logc（ab）/[logc(a)logc（b）]=31/[logc(a)

19.a^2>b>a>1,则logbb/a,logab从小到大依次为?∵a^2>b>a>1∴alog(a)=1,log(b)alog(b)a>logbb/a20.已知函数F（x）=|lgx|,若0b=

log(a+b)等于log(a+b),不要想太多

1(log43+log83)log32=(lg3/lg4+lg3/lg8)*(lg2/lg3)=lg3*(1/lg4+1/lg8)*(lg2/lg3)=(1/lg4+1/lg8)*lg2=lg2/lg

对数函数有这样的性质：log(A)M=log(b)M/log(b)A(b>0且b≠1）也称为换底公式故logac*logca=(lnc/lna)(lna/lnc)=1log23*log34*log45

这个明显不相等

ogax=2,即：a^2=x,则(a^2)^6=a^12=x^6logbx=3,即：b^3=x,则(b^3)^4=b^12=x^4logabcx=12,即：(abc)^12=x,则：(a^12)(b^

换底公式：logab=lgb/lgalog225×log34×log59=(lg25/lg2)×(lg4/lg3)×(lg9/lg5)=(2lg5/lg2)×(2lg2/lg3)×(2lg3/lg5)

设K=logab,那么我们有b=a^K,两边取以c为底数的对数有logcb=logca^K=Klogca,将logca除到左边即有K=logcb/logca而K=logab,所以公式得到推证.

设loga=m,a=10^mlogb=n,b=10^nab=10^(m+n)则logab=m+n=loga+log

loga(b)+longb(a)=lg(a)/lg(b)+lg(a)/lg(b)=-[lg(a)/lg(1/b)+lg(1/b)/lg(a)

∵logaN=b→a^b=N∴logmN=logm(a^b)∴logmN/logma=logm(a^b)/logma又∵logm(a^b)=b·logma∴logmN/logma=b·logma/lo

Logab=lgb/lgaLogbc=lgc/lgbLogca=lga/lgcLogab*logbc*logca=lgb/lga*lgc/lgb*/lgc=1

loga(3)=2=lg3/lga,logb(3)=4=lg3/lgblog(ab)(3)=lg3/(lga+lgb)=lg3/0.5lg3+0.25lg3=4/3

loga,logb,logc成等差数列则,2logb＝loga＋logc即,log(b²)＝log(ac)即,b²＝ac所以,a、b、c成等比数列b²＝ac