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    solving questions where the indice is unknown
    simple example being 5^x=125
    is trial and error the only method?
    coz i have more complicated ones to solve where
    something^x= surd
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    5^3 = 125

    Not sure if that's what you after.
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    no
    i want a method
    that was just a simple example
    if you got say 5^x= 10 root6 (again just an example)
    how's you go about that?
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    5^x = 125
    log5^x = log125
    x log5 = log 125
    x = log125/log5
    = 3

    logarithms

    Btw this is A2 maths so if you're only at GCSE you don't need to know that.

    In your more complicated example follow the same method to get x = 1.98731...
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    mik1a
    AS student
    haven't done log
    and we've been given the complicated example types?????
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    Well that's what I've picked up, I haven't done logs either but when you stay on these forums you learn some useful things

    I think that's the only way you can do it with complicated examples, unless your examples have x as a power on both sides, in which case you can change the actual number below the x to make them equal on either side and equate the xs:

    That wasn't very clear so here's an example:

    2^x = 8^(x-3)

    we know that 8=2^3

    so

    2^x = (2^3)^(x-3)
    2^x = 2^(3*(x-3))
    2^x = 2^(3x-9)

    then obviously

    x = 3x-9
    2x = 9
    x = 4.5

    You need to remember indices and surds rules and mess around with the equation to try to give you x=? If you weren't taught logs and are set those questions then there's probably some subtle way to do it.
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    Logs are in AS
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    P1 for OCR and AQA, P2 Edexcel I think.
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    (Original post by mik1a)
    P1 for OCR and AQA, P2 Edexcel I think.
    yup.

    if you ahvent done logs yet then trial and error is the way
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    What you need to do is get the bases's the same and then it becomes easy...

    So for example

    5^x = 125

    Make the bases equal...

    5^x = 5^3

    Now you can 'forget' about the fives so to speak, and look at just the powers. Therefore you get x = 3.

    This is the method explained by mik1a pretty much..
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    (Original post by imasillynarb)
    What you need to do is get the bases's the same and then it becomes easy...

    So for example

    5^x = 125

    Make the bases equal...

    5^x = 5^3

    Now you can 'forget' about the fives so to speak, and look at just the powers. Therefore you get x = 3.

    This is the method explained by mik1a pretty much..
    Thats the OCR P1 way, in logs dont come until OCR P2
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    (Original post by cobra01977)
    Thats the OCR P1 way, in logs dont come until OCR P2
    We learn that method in P1 and then learn logs in P2..for edexcel
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    You can also use clever tricks to change power and number:

    2√9 = |√4√9| = |√36| = 6
    12√8 = 3*0.25*√8 = 3√0.5√8 = 3√4
    10√9 = |√100√9| = |√900| = 30

    Cool huh
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    (Original post by mik1a)
    12√8 = 3*0.25*√8 = 3√0.5√8 = 3√4
    Uh???

    12√8 = 3*4*√8 = 3√128...if thats what you want.

    12√8 = 12(√4√2) = 24√2
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    (Original post by 2776)
    Uh???

    12√8 = 3*4*√8 = 3√128...if thats what you want.

    12√8 = 12(√4√2) = 24√2
    Yeah that's the one... 3*0.25 = 12?... :confused:
 
 
 
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