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问题: 不等式数列综合问题(难啊)

a>2,求证loga(a-1)<loga+1(a)

解答:

都大于0,求比值
loga(a-1)/loga+1(a) =loga(a-1)*loga(a+1)
<{[loga(a-1)+loga(a+1)]/2}^2
=[loga(a^-1)/2]^2
<{[loga(a^2)]/2}^2
=1
==>loga(a-1)<loga+1(a)

注意:1/loga+1(a) =loga(a+1)就可以了
比如1/lg100 =log100(10)