log以15为底的7=a,log以15为底的8=b,则log以56为底的15=log以3为底的7=a,则log以7为底的27

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log以15为底的7=a,log以15为底的8=b,则log以56为底的15=log以3为底的7=a,则log以7为底的27
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log以15为底的7=a,log以15为底的8=b,则log以56为底的15=log以3为底的7=a,则log以7为底的27
log以15为底的7=a,log以15为底的8=b,则log以56为底的15=
log以3为底的7=a,则log以7为底的27

log以15为底的7=a,log以15为底的8=b,则log以56为底的15=log以3为底的7=a,则log以7为底的27
log以56为底的15=log(56)[15],
对数函数换底公式log(a)[b]={log(p)[b]}/{log(p)[a]},
log(56)[15]
={log(15)[15]}/{log(15)[56]}
=1/{log(15)[7×8]}
=1/{log(15)[7]+log(15)[8]}
=1/(a+b),
log以3为底的7=a,则log以7为底的27:
log(7)[27]
={log(3)[7]}/{log(3)[27]}
=a/{log(3)[3³]}
=a/{3log(3)[3]}
=a/3