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    Im really stuck on the whole of question 4 on the jan 2000 paper
    Pleeeeeeease help me
    xox
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    (Original post by kindersurprise)
    Im really stuck on the whole of question 4 on the jan 2000 paper
    Pleeeeeeease help me
    xox
    Which is?
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    sorry,
    The first part is:
    f(x)=lnx and g(x)=x^2
    What is fg(x) and gf(x)
    xox
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    (Original post by kindersurprise)
    sorry,
    The first part is:
    f(x)=lnx and g(x)=x^2
    What is fg(x) and gf(x)
    xox
    fg(x)=ln(x^2)
    gf(x)=(lnx)^2
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    (Original post by kindersurprise)
    sorry,
    The first part is:
    f(x)=lnx and g(x)=x^2
    What is fg(x) and gf(x)
    xox
    Might help if you write f(g(x)) and g(f(x)).

    fg(x) = ln x^2
    gf(x) = (ln x)^2
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    Thanx, i guess im out of practice lol, not been doing any work over easter :eek:
    xox
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    (Original post by kindersurprise)
    sorry,
    The first part is:
    f(x)=lnx and g(x)=x^2
    What is fg(x) and gf(x)
    xox
    What is fg(x):

    g(x) = x^2:

    fg(x) = f(x^2) = ln(x^2) = 2lnx

    What is gf(x):

    f(x) = lnx

    gf(x) = g(lnx) = (lnx)^2
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    (Original post by Nylex)
    Might help if you write f(g(x)) and g(f(x)).

    fg(x) = ln x^2
    gf(x) = (ln x)^2
    For fg(x), wouldn't it be better to simplify further to 2lnx ?
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    (Original post by Ralfskini)
    fg(x)=ln(x^2)
    I think that 2lnx would be the better answer, as it goes that extra step in simplifying it.
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    (Original post by bono)
    I think that 2lnx would be the better answer, as it goes that extra step in simplifying it.

    Yeh, that bit is subjective.
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    (Original post by Ralfskini)
    Yeh, that bit is subjective.
    Sorry Ralf, just that my teacher always said to simplify lnx^n to nlnx
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    (Original post by bono)
    Sorry Ralf, just that my teacher always said to simplify lnx^n to nlnx

    No it's fine. Your way is probably better but the question is only going to be worth a mark anyway.
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    (Original post by Ralfskini)
    No it's fine. Your way is probably better but the question is only going to be worth a mark anyway.
    You'd be very suprised.

    For that whole question we just did (hardly took long, true), it would probably get us 4 marks.
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    (Original post by bono)
    You'd be very suprised.

    For that whole question we just did (hardly took long, true), it would probably get us 4 marks.
    Its 2 marks, but i needed to simlify to 2lnx for the next part of the qn
    Thanx for all your help
    xox
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    (Original post by kindersurprise)
    Its 2 marks, but i needed to simlify to 2lnx for the next part of the qn
    Thanx for all your help
    xox
    Really? Aaa, it's on your P2 Paper.

    "but i needed to simlify to 2lnx" - Yes, I did that in my solution, have a look. 2lnx was my final answer.

    On my syllabus we do it in P1. That question in P1 would probably collect me 4 marks, 3 at the very least.
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    (Original post by bono)
    Really? Aaa, it's on your P2 Paper.
    On my syllabus we do it in P1. That question in P1 would probably collect me 4 marks, 3 at the very least.
    I guess its just meant to be assumed knowledge for p2, so its not worth as many marks. We didnt have es and logs on p1 tho, which incidentaly i HATE lol
    xox
 
 
 
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