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+69
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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!
Guest Jan 25, 2012

Best Answer 

 #1
avatar+3065 
+25
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
admin  Jan 25, 2012
Sort: 

11+0 Answers

 #1
avatar+3065 
+25
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
+13
x=8,637
Guest Jan 25, 2012
 #8
avatar+442 
+10

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
+8

no, 8.637.

Guest Oct 26, 2014
 #5
avatar
+15

Woah, this is the first question ever asked!

Guest Jan 21, 2016
 #6
avatar+5197 
+10

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

rarinstraw1195  Mar 11, 2016
 #9
avatar+6880 
+15

The first question ever asked :O

It was hard

MaxWong  Apr 16, 2016
 #10
avatar+1823 
+10

First question ever asked!!

EighthMersennePrime  Aug 20, 2016
 #11
avatar
+10

YEEEEEEEEEEEEEEEEEEE!!!!! First question. Noice

Guest Oct 14, 2016
 #12
avatar+176 
+5

YOING First question nice

Sebast1ani5dumb  Dec 19, 2016
 #13
avatar+321 
0

Look what a hard first question!!!

Davis  Mar 3, 2017

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