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Log Question - 2004NC, #9 - HSN forum

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Log Question - 2004NC, #9


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#1 babeasc

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Posted 12 May 2007 - 04:00 PM

Solve the equation \log_{2}(x+1) - 2\log_{2}(3) = 3

<4 marks>




I just can't get the right answer!
Right answer ->
Spoiler

Any help appreciated!
x
Beyond it, and us, shines a greater hope and a brighter future
Can't wait 'til the exams are over!

#2 celticfcz

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Posted 12 May 2007 - 04:16 PM

QUOTE(babeasc @ May 12 2007, 05:00 PM) View Post
Solve the equation \log_{2}(x+1) - 2\log_{2}(3) = 3

<4 marks>




I just can't get the right answer!
Right answer ->
Spoiler

Any help appreciated!
x


Bring the 2 to the front to make it 3 to the power of 2 = 9

Then when its a minus you divide so its \log_{2}(x+1)/3 =3

Then you take your log2 over to the other side making it 2^3= 8

Then just a simple cross-multiply - 8x9 = 72
x+1 = 72
x=71

hope that helps - Im really bad at the maths formula things!

#3 babeasc

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Posted 12 May 2007 - 04:31 PM

Thanks for that...absolute lifesaver!

I always forget that rule where you turn

\log_{a}y = x

into

y=a^x

I always get it muddled up, needs more practice I think.

Once again, ta much tongue.gif
Beyond it, and us, shines a greater hope and a brighter future
Can't wait 'til the exams are over!

#4 celticfcz

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Posted 12 May 2007 - 04:33 PM

no problem wink.gif





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