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I'm stuck on the following question:
Express log2(x+2) - log2x as a single logarithm.
Hence solve the equation log2(x+2) - log2x = 3.
I can do part "a"- log2(x+2) - log2x = log2(x+2)/x
But how do I do part "b"?
Its probably so easy haha but anyway, +REP for any help :D
Oh and this is for C2 in case there are more advanced methods which you'd otherwise use :).
Okay, so we have:
log2((x+2)/x) = log((x+2)/x)/log(2) = 3
Multiply both sides by log(2);
log((x+2)/x) = 3log(2)
Take the exponential of both sides;
(x+2)/x = 8
Rearrange for x;
-7x = -2
x = 2/7
Oh right, I didn't realise that log2 (x) = log (x)/log2.Quote:
Originally Posted by Kardan
Do you know if that is a C2 concept? I've missed one lesson recently so maybe I missed that, although I can't see anything in the text book about it :S
If it isn't C2, do you know a way that uses a C2 method?
Im sure I told you that in Mod Spam? :SQuote:
Originally Posted by Matts
This video suggests it is a C2 MethodQuote:
Originally Posted by Matts
http://www.youtube.com/watch?v=zKV8Y...ure=plpp_video
Plus I can't think of any other methods that involve changing the base, and you will have to change the base in order to solve the equation.
Eh?Quote:
Originally Posted by Lee
In mod spam you said the following:
"Ouch" and (along the lines of) "No I can't do it"
haha
EDIT:
Right, thanks for your help :)Quote:
Originally Posted by Kardan
Out of curiosity, why did you bother changing the base? Why not just go:Quote:
Originally Posted by Kardan
log2(x+2 / x) = 3
x+2 / x = 23
In one step?
Just to show how to convert bases using the base conversion formula in C2.Quote:
Originally Posted by LoveToStack
I'd advise this method. Change of base is a C2 method but you don't need it here.Quote:
Originally Posted by LoveToStack