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Mathematics 7 Online
OpenStudy (anonymous):

log81^(3-8)^k

jimthompson5910 (jim_thompson5910):

can you draw this out?

OpenStudy (anonymous):

|dw:1317514216523:dw|

jimthompson5910 (jim_thompson5910):

so that -8 is not an exponent then?

OpenStudy (anonymous):

sorry it is the exponent of the 3 in paranthesis

jimthompson5910 (jim_thompson5910):

so it's really \[\Large \log_{81}\left(\left(3^{-8}\right)^k\right)\] ???

OpenStudy (anonymous):

yes

jimthompson5910 (jim_thompson5910):

\[ \Large \log_{81}\left(\left(3^{-8}\right)^k\right) \] \[ \Large \log_{81}\left(3^{-8k}\right) \] \[ \Large \frac{\log_{10}\left(3^{-8k}\right)}{\log_{10}\left(81\right)} \] \[ \Large \frac{\log_{10}\left(3^{-8k}\right)}{\log_{10}\left(3^4\right)} \] \[ \Large \frac{-8k\log_{10}\left(3\right)}{4\log_{10}\left(3\right)} \] \[ \Large \frac{-8k\cancel{\log_{10}\left(3\right)}}{4\cancel{\log_{10}\left(3\right)}} \] \[ \Large \frac{-8k}{4} \] \[ \Large -2k \] So \[ \Large \log_{81}\left(\left(3^{-8}\right)^k\right) = -2k \]

OpenStudy (anonymous):

excellent before i gave you good answer for this question, can you help me with this also d) 10^(5log10)^(8−8log10)^5))

jimthompson5910 (jim_thompson5910):

can you draw this out too? thx

OpenStudy (anonymous):

|dw:1317516390444:dw|

OpenStudy (anonymous):

jimthompson has a good answer. but if you have not gotten to change of base yet, note that \[3=81^{\frac{1}{4}}\]\]you can write \[\log_{81}(3^{-8k})=\log_{81}(81^{-2k})=-2k\] because

jimthompson5910 (jim_thompson5910):

So it's \[\Huge 10^{ 5\log_{10} \left( 8 \right) - 8\log_{10} \left( 5 \right) }\] ???

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