log (1\a) b -log (a) 1/b=?

来源:百度知道 编辑:UC知道 时间:2024/05/27 14:44:22
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首先介绍对数运算的换底公式:log(a)b=lgb/lga
证明:设log(a)b=t
则a^t=b,两边取以10为底的对数
lga^t=lgb
tlga=lgb
所以t=lgb/lga
所以log(a)b=lgb/lga

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log(1/a)b-log(a)1/b
=lgb/lg(1/a)-lg(1/b)/lga
=lgb/(-lga)-(-lgb)/lga
=-(lgb/lga)+(lgb/lga)
=0

log (1\a) b -log (a) 1/b
=lgb/[lg (1\a)]-lg(1/b)/lga
=-lgb/lga-lgb/lga
=-2lgb/lga