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base change

hi how do you change the base of this please to make same
logbase3 (2-3x) = logbase9 (2-3x)

how can u make the logbase 9 same as logbase 3?what formula thanks

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Reply 1
The formula is loga(x) = logb(x)/logb(a)
Reply 2
Original post by otrivine
hi how do you change the base of this please to make same
logbase3 (2-3x) = logbase9 (2-3x)

how can u make the logbase 9 same as logbase 3?what formula thanks


logab \displaystyle log_ab

We want to convert it into base c c

logab=logcblogca \displaystyle log_ab = \frac{log_cb}{log_ca}

Your question, log9(23x)=log3(23x)log39=log3(23x)log332=log3(23x)2log33=log3(23x)2 \displaystyle log_9 (2-3x) = \frac{log_3 (2-3x)}{log_39} = \frac{log_3 (2-3x)}{log_33^2} = \frac{log_3 (2-3x)}{2log_33} = \frac{log_3 (2-3x)}{2}
Reply 3
Original post by otrivine
hi how do you change the base of this please to make same
logbase3 (2-3x) = logbase9 (2-3x)

how can u make the logbase 9 same as logbase 3?what formula thanks


Use this
Reply 4
Original post by otrivine
hi how do you change the base of this please to make same
logbase3 (2-3x) = logbase9 (2-3x)

how can u make the logbase 9 same as logbase 3?what formula thanks


In this case 2-3x =1 this is so because the log terms must both be zero and the log of one is zero.

So x equals 1/3 The base 3 and base 9 are irrelevant.
Reply 5
got it guys thank you
Reply 6
Original post by steve2005
In this case 2-3x =1 this is so because the log terms must both be zero and the log of one is zero.

So x equals 1/3 The base 3 and base 9 are irrelevant.


and for binomial expanssion if for example (3-2x) power n
how do we work out n/?
Reply 7
Original post by otrivine
and for binomial expanssion if for example (3-2x) power n
how do we work out n/?


What does n/ mean?

(3-2x)^n what is the question?
Reply 8
Original post by steve2005
What does n/ mean?

(3-2x)^n what is the question?


like you are given with (3-2x) power n and they ask you to find n how do you do that?
Reply 9
Original post by otrivine
like you are given with (3-2x) power n and they ask you to find n how do you do that?


So you are given (3-2x)^7 and asked for the value of n. I would say the answer was seven.

Give us a REAL question and perhaps we can help.
Reply 10
(1+x/2)power n , where n is a postivie integer is 7 .
find the value of n
Reply 11
Original post by otrivine
like you are given with (3-2x) power n and they ask you to find n how do you do that?


(32x)n (3-2x)^n

With this much information it is impossible to find the value of 'n'.

The questions usually give some information about the coefficient of terms which allow to calculate it.
Reply 12
Original post by otrivine
(1+x/2)power n , where n is a postivie integer is 7 .
find the value of n


Did you invent this question?

Steve asked you to give a REAL question, you won't see such type of questions anywhere.
(edited 11 years ago)
Original post by otrivine
(1+x/2)power n , where n is a postivie integer is 7 .
find the value of n


I may be missing something BUT I can't see a question. I suggest you give a real question.
Reply 14
Original post by raheem94
Did you invent this question?


no mate its in the book page 77 mixed excersise 5E question 6)a)
Original post by otrivine
no mate its in the book page 77 mixed excersise 5E question 6)a)


I suggest you compare what you have written to what is printed in the book.
Reply 16
Original post by steve2005
I suggest you compare what you have written to what is printed in the book.


oh sorry :frown: but how do u do it please tell me sir
Reply 17
Original post by otrivine
no mate its in the book page 77 mixed excersise 5E question 6)a)


If you don't like to take your time writing you full question then i think we shouldn't waste our time on you.

Yesterday you said that a question is in the C2 jan 2012 paper, without telling the board.
Several times you have posted questions regarding the book, without telling which module you are talking about.

And right now the question you wrote wasn't complete.

Here is the question:





Don't mind, but i have tried to explain you several times to tell us the full question, if you talk about a book then tell the module, which book is it, and if exam paper remember to tell the board.
Reply 18
Original post by otrivine
oh sorry :frown: but how do u do it please tell me sir


For doing the question, just expand (1+x2)n \displaystyle \left( 1 + \frac{x}{2} \right)^n

Equate the coefficient of x2 x^2 in the expansion with 7.
Original post by otrivine
oh sorry :frown: but how do u do it please tell me sir


Are you asking for help or just messing about.

The question you posted is incomplete, please give the full question as printed in the book.

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