base change

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  1. otrivine's Avatar
    • TSR Legend
    • Posts: 14,642
    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
  2. Damask-'s Avatar
    • Benevolent Member
    • Location: Surrey
    • Posts: 892
    Re: base change
    The formula is loga(x) = logb(x)/logb(a)
  3. raheem94's Avatar
    • TSR Demigod
    • Posts: 5,512
    Re: base change
    (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
     \displaystyle log_ab

    We want to convert it into base  c

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

    Your question,  \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}
  4. steve2005's Avatar
    • TSR Demigod
    • Location: LONDON
    Re: base change
    (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
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  5. steve2005's Avatar
    • TSR Demigod
    • Location: LONDON
    Re: base change
    (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.
  6. otrivine's Avatar
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    • Posts: 14,642
    Re: base change
    got it guys thank you
  7. otrivine's Avatar
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    • Posts: 14,642
    Re: base change
    (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/?
  8. steve2005's Avatar
    • TSR Demigod
    • Location: LONDON
    Re: base change
    (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?
  9. otrivine's Avatar
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    • Posts: 14,642
    Re: base change
    (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?
  10. steve2005's Avatar
    • TSR Demigod
    • Location: LONDON
    Re: base change
    (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.
  11. otrivine's Avatar
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    • Posts: 14,642
    Re: base change
    (1+x/2)power n , where n is a postivie integer is 7 .
    find the value of n
  12. raheem94's Avatar
    • TSR Demigod
    • Posts: 5,512
    Re: base change
    (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?
     (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.
  13. raheem94's Avatar
    • TSR Demigod
    • Posts: 5,512
    Re: base change
    (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.
    Last edited by raheem94; 23-05-2012 at 20:46.
  14. steve2005's Avatar
    • TSR Demigod
    • Location: LONDON
    Re: base change
    (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.
  15. otrivine's Avatar
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    Re: base change
    (Original post by raheem94)
    Did you invent this question?
    no mate its in the book page 77 mixed excersise 5E question 6)a)
  16. steve2005's Avatar
    • TSR Demigod
    • Location: LONDON
    Re: base change
    (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.
  17. otrivine's Avatar
    • TSR Legend
    • Posts: 14,642
    Re: base change
    (Original post by steve2005)
    I suggest you compare what you have written to what is printed in the book.
    oh sorry but how do u do it please tell me sir
  18. raheem94's Avatar
    • TSR Demigod
    • Posts: 5,512
    Re: base change
    (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.
  19. raheem94's Avatar
    • TSR Demigod
    • Posts: 5,512
    Re: base change
    (Original post by otrivine)
    oh sorry but how do u do it please tell me sir
    For doing the question, just expand  \displaystyle \left( 1 + \frac{x}{2} \right)^n

    Equate the coefficient of  x^2 in the expansion with 7.
  20. steve2005's Avatar
    • TSR Demigod
    • Location: LONDON
    Re: base change
    (Original post by otrivine)
    oh sorry 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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