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    WHY ARE LOGARITHMS SO HARDDDDD.


    I've been practising for 12 hours and I still can't grasp it, especially when they ask for damn quadratic logs.

    I've been CRYING OVER THIS QUESTION!!!!


    Prove that if a^x = b^y = (ab)^xy, then x + y = 1


    I'M GOING INSANE X_X

    C2 exam... I'll see you in a retake.
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    (Original post by Lord Frieza)
    WHY ARE LOGARITHMS SO HARDDDDD.


    I've been practising for 12 hours and I still can't grasp it, especially when they ask for damn quadratic logs.

    I've been CRYING OVER THIS QUESTION!!!!


    Prove that if a^x = b^y = (ab)^xy, then x + y = 1


    I'M GOING INSANE X_X

    C2 exam... I'll see you in a retake.
    Are you sure that the question has two = signs
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    (Original post by Lord Frieza)
    WHY ARE LOGARITHMS SO HARDDDDD.


    I've been practising for 12 hours and I still can't grasp it, especially when they ask for damn quadratic logs.

    I've been CRYING OVER THIS QUESTION!!!!


    Prove that if a^x = b^y = (ab)^xy, then x + y = 1


    I'M GOING INSANE X_X

    C2 exam... I'll see you in a retake.
    There's a mistake in this question. x=y=0 is a counterexample.
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    (Original post by notnek)
    There's a mistake in this question. x=y=0 is a counterexample.
    +1.
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    I think it works if you assume that none of these hold:

    x=y=0
    a=b=1
    a=b=0
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    If you REALLY want to use logs... (as opposed to just exponents)

    Then you would log_ab everything. This would give you a new equation.

    Split the equation of three into two equation of twos, do some VERY simple algebra to each, and everything you want will come easily.
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    There's no mistake in the question, it's a standard exam style question written exactly like that, can anyone write down a worked solution??!?!?!
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    Please follow the hint I gave and show your working so we can nudge you should you get stuck.

    Full solutions are boring.
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    (Original post by notnek)
    The question does have mistakes and is definitely not a C2 exam question.

    Where did you get the question from? My advice: if the question is making you go insane, give up. Focus on real C2 exam questions.
    It's from the edexcel textbook I saw it the other day
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    a^x = b^y = (ab)^xy, then x + y = 1

    a^x - b^y = (ab)^xy, then x + y = 1

    = (Loga + Logb)^xy = Xloga - ylogb

    I am so confused..
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    (Original post by notnek)
    The question does have mistakes and is definitely not a C2 exam question.

    Where did you get the question from? My advice: if the question is making you go insane, give up. Focus on real C2 exam questions.
    It's in the official edexcel C2 book. Mixed exercise 3G Q10. There's no mistake.
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    (Original post by SheldonWannabe)
    It's in the official edexcel C2 book. Mixed exercise 3G Q10. There's no mistake.
    Yeaah that's the one!

    Edit: There's a big fat 'E' next to it.. as in EXAM QUESTION.
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    (Original post by Lord Frieza)
    Yeaah that's the one!
    I know it off by heart because that's the one logs questions I can't do either. :banghead:
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    (Original post by SheldonWannabe)
    It's in the official edexcel C2 book. Mixed exercise 3G Q10. There's no mistake.
    As I showed in my first post, if it's written as the OP posted it, it's wrong.
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    (Original post by SheldonWannabe)
    I know it off by heart because that's the one logs questions I can't do either. :banghead:
    You can do the other 11 questions..?\

    They are so hard for me
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    (Original post by notnek)
    As I showed in my first post, if it's written as the OP posted it, it's wrong.

    Dude. -.-
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    (Original post by Lord Frieza)
    Yeaah that's the one!

    Edit: There's a big fat 'E' next to it.. as in EXAM QUESTION.
    Most likely it has been copied from an exam incorrectly.

    Can you explain why you negged me? Try inputting x=y=0 and a=b=1.
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    (Original post by Lord Frieza)
    Yeaah that's the one!
    if a^x=b^y=(ab)^{xy} then a^x=b^y take logs from both sides and form in terms of y and x an expression for a log, base a and b log_abthen get another expression in terms of x and y =x and then find an expression for log_a using a^x=(ab)^{xy} where you need to remember that xlog_aa=x
    If your stuck here's a bit of guidance for forming your first equation
    Spoiler:
    Show
    log_a(a^{x})=log_a(b^{y}) (use the power rule)
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    Yeah I remember this question in my Edexcel C2 book, it got me as well.
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    (Original post by notnek)
    Most likely it has been copied from an exam incorrectly.

    Can you explain why you negged me? Try inputting x=y=0 and a=b=1.
    I didn't neg you, but even on the cd it's the same question. There's no mistake whatsoever!
 
 
 
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