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Mathematics 10 Online
OpenStudy (mathlegend):

Logarithm... write with same base

OpenStudy (mathlegend):

\[\log _{2}12+\log _{4}6-\log _{2}24\]

OpenStudy (mathlegend):

So obviously I start with the middle log... that has the base of 4 to change it to base 2... \[4^{x}=6\] \[(2^{2})^{x}=6\] \[2^{2x}=6\]

OpenStudy (mathlegend):

Which means... \[\log _{2}6=2x\]

OpenStudy (mathlegend):

How do I simplify this even more?

OpenStudy (mathlegend):

I know the answer is... \[\frac{ 1 }{ 2 }\log _{2}6 = \log _{2}6^{\frac{ 1 }{ 2 }}\]

OpenStudy (mathlegend):

I just don't know how you jump to that...

myininaya (myininaya):

@MathLegend Try to combine what you can for now Then simplify it

myininaya (myininaya):

use the division property first log(a)-log(b)=log(a/b) for the ones that have the same base

OpenStudy (mathlegend):

ok

OpenStudy (mathlegend):

\[\log _{2}(\frac{ 12 }{ 24 })+\log _{4}6\]

myininaya (myininaya):

great so far but 12/24 reduces

OpenStudy (mathlegend):

Oh, I wasn't sure if we were allowed to reduce.. because my teacher never does with logs. \[\log _{2}(\frac{ 1 }{ 2 })+\log _{4}6\]

myininaya (myininaya):

ok so that 1/2 is very important here because you know log_2(1)=? and you know log_2(2)=?

myininaya (myininaya):

\[\log_2(\frac{1}{2})=\log_2(1)-\log_2(2)=? \]

OpenStudy (mathlegend):

-1 ?

myininaya (myininaya):

so you have \[-1+\log_4(6) \]

myininaya (myininaya):

now if you want to write this as one log with one base you can

myininaya (myininaya):

\[1=\log_a(a)\]

myininaya (myininaya):

where a>0 and not equal to 1 of course :)

OpenStudy (mathlegend):

Okay, so should I do what I did earlier to have this change to... \[2^{2x}=6 = \log _{2}6=2x\]

OpenStudy (mathlegend):

\[\log _{2}6=2x\]

myininaya (myininaya):

You don't need that do you mean 2^(2x)=6 implies log_2(6)=2x

myininaya (myininaya):

replace the 1 in your problem with log_4(4) so the bases will match

myininaya (myininaya):

\[-1+\log_4(6)=-\log_4(4)+\log_4(6)=\log_4(6)-\log_4(4)\] you should be able to take it from here

OpenStudy (mathlegend):

\[\log _{4}(\frac{ 3 }{ 2 })\]

myininaya (myininaya):

that's great

OpenStudy (mathlegend):

But the answer says... \[\log _{2}(\frac{ \sqrt{6} }{ 2 })\]

myininaya (myininaya):

it looks like they also wrote it with base 2 instead of base 4 so if you want it in base 2 you will need to play with our answer some more

myininaya (myininaya):

\[\log_4(\frac{3}{2})=\frac{\log_2(\frac{3}{2})}{\log_2(4)} \text{ (By change of base formula ) }\] \[=\frac{\log_2 (\frac{3}{2})}{\log_2(2^2)}\] do you got from here?

OpenStudy (mathlegend):

I'm confused on how you just went from base 4 to base 2 in the numerator and the denominator... because isn't the formula... \[\log _{b}M=\frac{ logM }{ logb }\]

OpenStudy (mathlegend):

\[\frac{ \log4 }{ \log \frac{ 3 }{ 2 } }\]

OpenStudy (mathlegend):

Am I utilizing the formula incorrectly?

myininaya (myininaya):

Ok sorry was eating... but yeah the formula is \[\log_b(M)=\frac{\log_a(M)}{\log_a(b)}\] We want a to be 2 so I replaced a's with 2 M was 3/2 to I replaced M with 3/2 everywhere else b was 4 so I replaced all the b's with 4

myininaya (myininaya):

|dw:1398543261227:dw| when comparing these two you should see that..

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