loga/logb等于

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)

log(ab)abc=log(ab)ab+log(ab)c=1+1/log(c)ab=1+1/[log(c)a+log(c)b]=1+1/[1/log(a)c+1/log(b)c]=1+log(a)c

loga(m)+logb(m)=3=1/logm(a)+1/logm(b),loga(m)*logb(m)=1=1/[logm(a)*logm(b)],第一个表达式通分得logm(a)+logm(b)

设x=logbN则有b^x=N两边取以a为底的对数logab^x=logaNxlogab=logaNx=(logaN)/(logab)即logbN=(logaN)/(logab)利用上面证明的公式,很

1.（lgx）^2-lg(x^2)-2=0得（lgx）^2-2lgx-2=0维达定理lga*lgb=-2lga+lgb=2logab+logba=lgb/lga+lga/lgb=[(lga）^2+(l

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=

lg[（a+b）/3]=lg(a+b)-lg3这样写才对,你那个没底数![lga+lgb]/2=[lg(ab)]/24a^2+9b^2-13ab=0(2a+3b)^2-ab=0

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

呵呵换底公式啦解上面方程lgx=3或lgx=-1不妨设lga=3或lgb=-1logab=(lgb)/(lga)=-1/3logba=(lga)/(lgb)=-3两个一加就是-10/3啦换底公式是对数

这个明显不相等

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)

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