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Mathematics 7 Online
OpenStudy (anonymous):

logs

OpenStudy (zepp):

Dance dance dance

OpenStudy (anonymous):

bricks

OpenStudy (zepp):

aluminium bars

OpenStudy (anonymous):

\[\log_{9} (1/3)\]

OpenStudy (anonymous):

hahah yall are to funny!

OpenStudy (zepp):

Are you allowed to use a calculator?

OpenStudy (anonymous):

yess

OpenStudy (zepp):

Familiar with change of base formula?

OpenStudy (anonymous):

nopeee

OpenStudy (anonymous):

zepp formula will always work and good if you are trying to get and answer quick and not worry too much but don't forget that \[\log_b(x)=y\iff b^y=x\]and you should be able to switch back and forth quicklyi

OpenStudy (anonymous):

\[\log_9(\frac{1}{3})=y\iff 9^y=\frac{1}{3}\] if you can solve this you are in good shape if not, you need to get familiar with exponents

OpenStudy (anonymous):

you should be thinking "9 to what power gives \(\frac{1}{3}\) ?"

OpenStudy (anonymous):

yes i can get myself to this point.. I just need to get familiar with exponents.. ha but really i need help with the last part you said

OpenStudy (anonymous):

ok as long as you recognize that is the crux of the problem now we can think, how can i get from 9 to \(\frac{1}{3}\) only using EXPONENTS i.e not multiplying or dividing or anything like that

OpenStudy (zepp):

hint \(\sqrt{x}=x^\frac{1}{2}\)

OpenStudy (anonymous):

first off it is pretty clear that the square root of 9 is 3 right? now we recall that we can write \(\sqrt{9}=3\) or \(9^{\frac{1}{2}}=3\)

OpenStudy (zepp):

And forget the fraction 9 to the power of what gives ^3

OpenStudy (anonymous):

3?

OpenStudy (anonymous):

that gets us the 3, now we need the reciprocal

OpenStudy (anonymous):

3/1

OpenStudy (zepp):

Reciprocal of the exponent

OpenStudy (anonymous):

opps 1/3

OpenStudy (zepp):

\[\large 9^\frac{1}{2}=\sqrt{9}=3\]

OpenStudy (zepp):

Reciprocal of the exponent, not the result D:

OpenStudy (zepp):

We have to do something so 3 becomes \(\frac{1}{3}\)

OpenStudy (anonymous):

okay.. im getting confused here 2/1? idk

OpenStudy (zepp):

Therefore -1/2

OpenStudy (anonymous):

sorry i just get confused with all these terms :/

OpenStudy (anonymous):

might i make a suggestion? because it looks like you are confused as to where to focus we have \[\log_b(x)=y\iff b^y=x\] so for example \[10^2=100\iff \log_{10}(100)=2\] \[5^3=125\iff \log_5(125)=3\] \[10^{-3}=0.001\iff \log_{10}(0.001)=-3\] \[36^{\frac{1}{2}}=6\iff\log_{36}(6)=\frac{1}{2}\] \[4^{-1}=\frac{1}{4}\iff \log_4(\frac{1}{4})=-1\] and so one what you need to focus on is the exponent

OpenStudy (anonymous):

therefore when you see \[\log_9(\frac{1}{3})=y\] you think \[9^y=\frac{1}{3}\] a minus sign with give you the reciprocal and the one half will give you the square root, so your answer is minus one half

OpenStudy (zepp):

I wish I can explain that well @satellite73 :P

OpenStudy (anonymous):

YAY! no @zepp you can explain very well i just get confused because everything was spread all over the place.. but what i do want to learn is how you got -1/2?

OpenStudy (zepp):

:o Thanks :) And for the reciprocal thing, it's very easy Here \[4^1=4\] right?

OpenStudy (anonymous):

yesss

OpenStudy (zepp):

Alright! What you have to remember that if the exponent is negative, it will flip the number(or fraction) \[4^-1=\frac{1}{4}\]

OpenStudy (zepp):

\[4^{-1}=\frac{1}{4}\] sorry

OpenStudy (anonymous):

its okay, i understood ha

OpenStudy (zepp):

Great! :D ░░░░░░░░░░░░▄▄ ░░░░░░░░░░░█░░█ ░░░░░░░░░░░█░░█ ░░░░░░░░░░█░░░█ ░░░░░░░░░█░░░░█ ███████▄▄█░░░░░██████▄ ▓▓▓▓▓▓█░░░░░░░░░░░░░░█ ▓▓▓▓▓▓█░░░░░░░░░░░░░░█ ▓▓▓▓▓▓█░░░░░░░░░░░░░░█ ▓▓▓▓▓▓█░░░░░░░░░░░░░░█ ▓▓▓▓▓▓█░░░░░░░░░░░░░░█ ▓▓▓▓▓▓█████░░░░░░░░░█ ██████▀░░░░▀▀██████▀

OpenStudy (anonymous):

how did you do that????

OpenStudy (zepp):

hax

OpenStudy (anonymous):

but to get 1/2 in general.. was it just guess and check? or what

OpenStudy (zepp):

Haha http://fb-art.blogspot.ca/2011/08/big-cool-facebook-like-thumb-special.html there you go :P

OpenStudy (zepp):

Nope, since the square root of 9 is 3, squareroot also means ^1/2, and we want the 3 flipped, so we add a negative sign, -1/2

OpenStudy (anonymous):

in a way it is a guess, but an educated guess you have 9 as the base and you see a 3 you get from 9 to 3 by taking the square root, and you can write the square root as an exponent

OpenStudy (anonymous):

of course you can also get from 9 to 3 by a) subtracting 6 b) dividing by 3 c) etc etc but you want something that you can write as an exponent, like taking powers, roots, and reciprocals

OpenStudy (anonymous):

so i would say "educated guess" and practice with exponents

OpenStudy (anonymous):

THANK YOU BOTH! YAY! i understand it now!!!

OpenStudy (anonymous):

..oh forsure! ha

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