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3^(x+1)=4^(x-1)

Solve for x! Can't for the life of me figure this out! I assume you have to use Logs!
 Jan 25, 2012

Best Answer 

 #1
avatar+3144 
+48
3^(x+1)=4^(x-1) | *4

4*3^(x+1)=4^x

ready?

4*3^(x+1)=4^x | ln( .. ) on both sides, let's assume x will be larger 0

ln( 4*3^(x+1) ) = ln( 4^x )

x*ln(3)+ln(12) = x*ln(4) | -x*ln(4) and -ln(12)

x*ln(3)-x*ln(4)=-ln(12)

x*(ln(3)-ln(4))=-ln(12)

x=-ln(12)/(ln(3)-ln(4))

x ≈ 8.63768335861279
 Jan 25, 2012
 #1
avatar+3144 
+48
Best Answer3^(x+1)=4^(x-1) | *4

4*3^(x+1)=4^x

ready?

4*3^(x+1)=4^x | ln( .. ) on both sides, let's assume x will be larger 0

ln( 4*3^(x+1) ) = ln( 4^x )

x*ln(3)+ln(12) = x*ln(4) | -x*ln(4) and -ln(12)

x*ln(3)-x*ln(4)=-ln(12)

x*(ln(3)-ln(4))=-ln(12)

x=-ln(12)/(ln(3)-ln(4))

x ≈ 8.63768335861279
admin Jan 25, 2012
 #2
avatar
+18
x=8,637
 Jan 25, 2012
 #8
avatar+425 
+15

They use a comma for a decimal point.

 

To avoid confusion, for a thousand, no need for a separator, use a space to separate.

 

1 234 = 1 thousand 2 hundreds 3 tens 4 ones

1,234 or 1.234 = 1 one 2 tenths 3 hundredths 4 thousandths

MWizard2k04  Apr 7, 2016
 #3
avatar
+13

no, 8.637.

 Oct 26, 2014
 #5
avatar
+24

Woah, this is the first question ever asked!

 Jan 21, 2016
 #6
avatar+5265 
+19

And here we have the first question ever asked. It was asked on Jan. 25, 2012. Wonderful question.

 Mar 11, 2016
 #9
avatar+9665 
+27

The first question ever asked :O

It was hard

 Apr 16, 2016
 #10
avatar+1886 
+16

First question ever asked!!

 Aug 20, 2016
 #11
avatar
+17

YEEEEEEEEEEEEEEEEEEE!!!!! First question. Noice

 Oct 14, 2016
 #12
avatar+180 
+13

YOING First question nice

 Dec 19, 2016
 #13
avatar+501 
+9

Look what a hard first question!!!

Davis  Mar 3, 2017

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