Friday, March 4, 2016

logarithms - Problems simplifying logarithmic expressions

I learned all the scripts provided, yet I simply cannot find a way to simplify the following equations:







4log29
What I've thought so far: 9 may be written as 32, so maybe we could do something with the base log2, but therefore it would have to be 23, not the other way round - cannot think of any other approach.



EDIT: See How alogbx=xlogba? top answer (basically it explains how to transform alogb(x) to xlogb(a))







813log64
What I've done so far: 81/3=2813log64=2log64 - but I have no idea how to simplify this term. (Maybe something with 4=22 and 6=32 and do something with the 2s, but I don't know of any rule that allows you to "split" bases)



EDIT: turned out to be a typo, it should have read like this 813log24 which basically is 22=4






e12log9
No idea what to do here. (Maybe try to "bring down" the natural logarithm, but how?)




EDIT:
e12log9=912log9 log9e =912log99log9elog9e =3
In words: change base, then change base in the exponent and cancel (can you put it like that in English?) so that only 3 remains.







b4logbx
Same like above - try to bring down the logarithm with the base b.



EDIT: (In thoughts) isolate the log, so that blogbx remains this is x the final result should be $x^4.






e3log 8x
Same here with natural logarithm again.




EDIT: Same like the previous example, final result should be (8x)3.






To prevent any misunderstandings: I'm not asking for solutions or step-by-step-instructions, just want to know if I'm heading in the right direction and if there's any rule/approach I overlooked which can be applied here. (Sadly we didn't do much logarithm-related stuff in school and at university it's considered to be foreknowledge, so they don't explain it any more)

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