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Mathematics 25 Online
OpenStudy (anonymous):

What is the value of

OpenStudy (anonymous):

\[\log_{81} 3\]

OpenStudy (anonymous):

@UsukiDoll

OpenStudy (anonymous):

@DecentNabeel

OpenStudy (decentnabeel):

\[\log _{81}\left(3\right)=\frac{1}{4}\quad \left(\mathrm{Decimal:\quad }\:0.25\right)\]

OpenStudy (anonymous):

@satellite73

OpenStudy (decentnabeel):

Happy:) @EllenJaz17

OpenStudy (anonymous):

how do you value that though? I have to show my work

OpenStudy (anonymous):

@DecentNabeel

OpenStudy (decentnabeel):

\[\mathrm{Rewrite\:}3\mathrm{\:\in\:power-base\:form:}\quad 3=81^{\frac{1}{4}}\] \[=\log _{81}\left(81^{\frac{1}{4}}\right)\] \[\mathrm{Apply\:the\:\log\:rule}:\quad \log _a\left(x^b\right)=b\cdot \log _a\left(x\right)\] \[\log _{81}\left(81^{\frac{1}{4}}\right)=\frac{1}{4}\log _{81}\left(81\right)\] \[=\log _{81}\left(81\right)\frac{1}{4}\] \[\mathrm{Apply\:the\:\log\:rule}:\quad \log _a\left(a\right)=1\] \[\log _{81}\left(81\right)=1\] =1/4

OpenStudy (decentnabeel):

ok @EllenJaz17

OpenStudy (anonymous):

\[\log_{81}(3)=x\iff 81^x=3\] so what you are trying to do is figure out how to write 3 as a power of 81 since \(\sqrt[4]{81}=3\) that tells you \[81^{\frac{1}{4}}=3\] and you have the power you are looking for

OpenStudy (anonymous):

so it's not 1/4 its 3?

OpenStudy (anonymous):

another easier example \[\log_7(49)=2\] because \(7^2=49\)

OpenStudy (anonymous):

no the answer is \(\frac{1}{4}\) let me write it again

OpenStudy (anonymous):

ok sounds good

OpenStudy (anonymous):

\[\huge \log_{81}(\color{red}x)=3\iff 81^{\color{red}x}=3\] you are trying to find \(\color{red}x\)

OpenStudy (anonymous):

you are looking for the power that you would raise 81 to to give you 3

OpenStudy (anonymous):

\[\log_2(8)=3\iff 2^3=8\] they say the same thing

OpenStudy (anonymous):

you should be able to switch back and forth quickly

OpenStudy (anonymous):

the only tricky part of this one was recognizing that 3 is the fourth root of 81

OpenStudy (anonymous):

.sorry catching up was getting something to drink

OpenStudy (anonymous):

beer i hope

OpenStudy (anonymous):

haha no just water

OpenStudy (anonymous):

too bad

OpenStudy (anonymous):

I prefer straight tequila, gets the job done quick lol

OpenStudy (anonymous):

no beer chaser? dang!

OpenStudy (anonymous):

Haha nope!

OpenStudy (anonymous):

oops do you get that \(2^5=32\) says the same thing as \(\log_2(32)=5\) ?

OpenStudy (anonymous):

how would i apply that to find this value in my question?

OpenStudy (anonymous):

so if you were trying to solve \[\log_2(32)=\color{red}x\] you would be trying to solve \[2^{\color{red}x}=32\]

OpenStudy (anonymous):

you have \[\log_{81}(3)=\color{red}x\] you have to solve \[81^{\color{red}x}=3\]

OpenStudy (anonymous):

since \(\sqrt[4]{81}=x\) that is the same think as saying \(81^{\frac{1}{4}}=3\)

OpenStudy (anonymous):

ooops i means "since \(\sqrt[4]{81}=3\)

OpenStudy (anonymous):

now you have the power you are looking for , that power is \(\frac{1}{4}\) therefore since \[81^{\frac{1}{4}}=3\] it is the same as saying \[\log_{81}(3)=\frac{1}{4}\]

OpenStudy (anonymous):

Ok i kinda get it lol

OpenStudy (anonymous):

yeah it is confusing at first a simpler example is it clear that \(10^4=10,000\)?

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