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Mathematics 17 Online
OpenStudy (anonymous):

I need help!!

OpenStudy (anonymous):

\[\log_{6} (3x+2)=\log_6(x+4)+1\]

OpenStudy (anonymous):

@LarsEighner can you help?

OpenStudy (larseighner):

For a start, I'd put all the log terms on one side.

OpenStudy (anonymous):

what I thought I was suppose to do since both sides have the same base

OpenStudy (anonymous):

the we inverse it or something

OpenStudy (larseighner):

What does log a - log b mean? What is it equal too?

OpenStudy (anonymous):

log(a/b)?

OpenStudy (larseighner):

Right. Now how to express 1 as a log of the same base?

OpenStudy (anonymous):

wait what?

OpenStudy (larseighner):

1 = log_6( ?) In other words, convert the 1 to log_6

OpenStudy (anonymous):

wouldnt it be 1=log_6(x)?

OpenStudy (anonymous):

i have no clue

OpenStudy (larseighner):

No. What is log_6(6) ?

OpenStudy (anonymous):

what do you want me to do, isn't that just like true? log_6(6) is true

OpenStudy (anonymous):

im not sure what your asking here

OpenStudy (larseighner):

Replace the 1 in your equation with log_6(something). You should know what something is.

OpenStudy (larseighner):

\[ \large \log_{6} (3x+2)=\log_6(x+4)+1 \] You did this: \[ \large \log_{6} (3x+2) - \log_6(x+4) = 1 \] And you knew you could replace the difference of the logs with \[ \large \log_{6} {(3x+2\over (x+4)} = 1 \] Now I am saying replace the 1 on the right with its value as a log base 6.

OpenStudy (anonymous):

Actually what I did was this, (not sure if correct or not) \[6^{\log(3x+2)}=6^{\log(x+4)+1}\] then 3x+2=(x+4)+1 3x+2=x+5 3x-x=5-2 2x=3 x=3/2

OpenStudy (anonymous):

did i do it right?

OpenStudy (anonymous):

wait why is it 22/7, when you are dividing the -3 not 7?

OpenStudy (anonymous):

it would be 22/-3, at least thats what you are trying to say there

OpenStudy (anonymous):

but that isn't the final answer right?

OpenStudy (larseighner):

\begin{align} \large \log_{6} {{(3x+2)}\over {(x+4)}} &= 1 \cr \log_{6} {{(3x+2)}\over {(x+4)}} &= log_6 6 \cr {{(3x+2)}\over {(x+4)}} &= 6 \cr (3x+2) &= 6 (x+4) \cr 3x+2 &= 6x+24\cr -3x &= 22 \cr x &= -{22 \over 3}\cr\end{align}

OpenStudy (anonymous):

and thats it?

OpenStudy (anonymous):

cause if so, i'm not understanding how you got the log_6 (3x+2)/(x+4)=1

OpenStudy (anonymous):

Do you know anyone else that might help explain this to me?

OpenStudy (anonymous):

@LarsEighner

OpenStudy (larseighner):

We got to that step because log a - log b = log (a/b) for any base

OpenStudy (larseighner):

@SolomonZelman I think I went wrong here somehow. Would you look it over?

OpenStudy (larseighner):

@mathstudent55 ?

OpenStudy (anonymous):

it uh says they are offline.. @LarsEighner

OpenStudy (larseighner):

\[\large \log_{6} (3x+2)=\log_6(x+4)+1\] \[\large \log_{6} (3x+2)-\log_6(x+4) =1\] \[\large \log_{6} {{3x+2} \over {x+4}} = log_6 6\] \[\large {{3x+2} \over {x+4}} = 6\] \[\large 3x+2 =6 (x+4) \] \[\large 3x+2 =6x+24 \] \[\large 3x=6x+22) \] \[\large -3x=22 \] What's bothering me is it is negative. \[\large x=- {22 \over 3}\]

OpenStudy (larseighner):

@thomaster ?

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