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Logarithms

Hello,

Could someone please help me with this problem step by step - not sure how tou get to the answer - can only get so far and :-(

11a) Show that log[4]3 = log[2]sqrt3

11b) Hence or otherwise solve the simultaneous equation:

2log[2]y = log[4]3 + log[2]x

3^y = 9^x

Thanks for you help!
Original post by christinajane
Hello,

Could someone please help me with this problem step by step - not sure how tou get to the answer - can only get so far and :-(

11a) Show that log[4]3 = log[2]sqrt3

11b) Hence or otherwise solve the simultaneous equation:

2log[2]y = log[4]3 + log[2]x

3^y = 9^x

Thanks for you help!


How did you get on with 11a? :h:
Original post by SeanFM
How did you get on with 11a? :h:


I got, which I don't even know if its right :

log[4]3 = 1/2log[2]3 = log[2]3^1/2 = log[2]sqrt3

Which seems too obvious????
Reply 3
Original post by christinajane
I got, which I don't even know if its right :

log[4]3 = 1/2log[2]3 = log[2]3^1/2 = log[2]sqrt3

Which seems too obvious????


It's correct! Keep going.
Reply 4
too late ...
Oops forgot first line - log[4]3 = log[2]3/log[2]4 = log[2]3/2

but dont really now why that eqals log[2]sqrt3??
Reply 6
Original post by christinajane
I got, which I don't even know if its right :

log[4]3 = 1/2log[2]3 = log[2]3^1/2 = log[2]sqrt3

Which seems too obvious????


There is a rule you can use to change the base of a logarithm.
loga(b)=[logc(b)]/[logc(a)].
(edited 8 years ago)
Second part I get -

2log[2]y = log[4]3 + log[2}x 3^y = 9^x
y = 2^x (2)
log[2]y^2 = log[2]sqrt3 + log[2]x

y^2 = x(sqrt3) (1)


It follows that:

substituting equation 2 into 1

(2^x)^2 = xsprt3

4x^2 = xsqrt3


then I get stuck...

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