Logarithmic Function Help

sarav7

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Joined
Dec 6, 2011
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1/3(6)^(-4x)+1=6

I got an answer, but checked it in the back of the book and it was wrong. Here is what I did:

1/3(6)^(-4x)=5
6^-4x=15
log base 6 of 15 =-4x
log6/log15=-4x
-.165=x

The right answer is -.378
 
1/3(6)^(-4x)+1=6

I got an answer, but checked it in the back of the book and it was wrong. Here is what I did:

1/3(6)^(-4x)=5
6^-4x=15
log base 6 of 15 =-4x
log6/log15=-4x
-.165=x

The right answer is -.378

Ok...what you have is correct to this point:

6-4x = 15

Now, how about taking the log of both sides (I'll use natural logs):

ln 6-4x = ln 15

Use one of the rules of logs: ln bn = n ln b

(-4x) ln 6 = ln 15

x * -4 ln 6 = ln 15

Divide both sides by (-4 ln 6):

x = ln 15 / (-4 ln 6)
 
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