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    (Original post by raheem94)
    Yes, you did it correctly and got the correct answer .
    Thats the piece of work I'm doing, for future reference.
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  1. File Type: doc C2_-_50_Questions.doc (111.0 KB, 44 views)
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    (Original post by King-Panther)
    What would I sub in to get 0? Or do I not have to do that??
    I have seen the microsoft word file. You question is done, you don't need to do anything further.
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    (Original post by raheem94)
    I have seen the microsoft word file. You question is done, you don't need to do anything further.
    The next question, I got dy/dx = 12x + 5

    So when gradient is 13, I did

    13 = 12x + 5

    which is x = 2/3



    I dont understand Q)15.
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    (Original post by King-Panther)
    The next question, I got dy/dx = 12x + 5

    So when gradient is 13, I did

    13 = 12x + 5

    which is x = 2/3
    You are starting to grasp the concepts .

    This is correct as well, i also get the same answer.
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    (Original post by raheem94)
    You are starting to grasp the concepts .

    This is correct as well, i also get the same answer.
    I know how to do them, I just didn't understand the wording..

    I don't understand what they want for Q)15
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    (Original post by King-Panther)
    I dont understand Q)15.

    Do you know integration?
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    (Original post by raheem94)
    Do you know integration?
    Yeah

    I got x^4-x-2

    Also, what is d2y/dx2 of x^2+2+1/x^2
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    (Original post by King-Panther)
    Yeah

    I got x^4-x-2
    So you got,  \displaystyle x^4 - x^{-2} , right?

    But we need to add a constant of integration, c, because it is a indefinite integral.

    So  \displaystyle y= x^4 - x^{-2} + c

    Now use the conditions given in the question of y=17 and x=2 to find the value of 'c'.
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    (Original post by King-Panther)
    Yeah

    I got x^4-x-2
    +c

    Then sub in the numbers as given in the question.

    You're probably best off creating your own thread for these questions.
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    (Original post by raheem94)
    So you got,  \displaystyle x^4 - x^{-2} , right?

    But we need to add a constant of integration, c, because it is a indefinite integral.

    So  \displaystyle y= x^4 - x^{-2} + c

    Now use the conditions given in the question of y=17 and x=2 to find the value of 'c'.
    So 17=2^4-2^-2+c

    Also, what is d2y/dx2 of x^2+2+1/x^2
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    (Original post by Zuzuzu)
    +c

    Then sub in the numbers as given in the question.

    You're probably best off creating your own thread for these questions.
    I did, but it was suggested this was the best place for me...
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    (Original post by King-Panther)
    So 17=2^4-2^-2+c

    Also, what is d2y/dx2 of x^2+2+1/x^2
     \displaystyle y= x^4 - x^{-2} + c

    Sub in y=17 and x=2 in the above expression, to find the 'c'.
     17 = 2^4 - 2^{-2} + c \implies 17=16- \frac14+c \implies c=\frac54

    So  \displaystyle y=x^4-x^{-2}+\frac54

    You don't need to find d2y/dx2.
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    (Original post by raheem94)
     \displaystyle y= x^4 - x^{-2} + c

    Sub in y=17 and x=2 in the above expression, to find the 'c'.
     17 = 2^4 - 2^{-2} + c \implies 17=16- \frac14+c \implies c=\frac54

    So  \displaystyle y=x^4-x^{-2}+\frac54

    You don't need to find d2y/dx2.
    Also, what is d2y/dx2 of x^2+2+1/x^2

    Also, how about Q)16, b? Do I treat it as a quadratic?

    I really appreciate this!
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    (Original post by King-Panther)
    I did, but it was suggested this was the best place for me...
    Its better you use your previous thread, 'integration', or make a new thread don't post in this thread.
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    (Original post by King-Panther)
    Also, what is d2y/dx2 of x^2+2+1/x^2

    Also, how about Q)16, b? Do I treat it as a quadratic?

    I really appreciate this!
    Treat 16b as a quadratic. And please don't post in this thread, use your previous thread again or make a new thread.
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    Can anyone help me?

    http://www.thestudentroom.co.uk/show...1960422&page=7
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    help please?

    http://www.thestudentroom.co.uk/show....php?t=1970327
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    Question: If you choose an answer to this question at random, what is the probability that you will be correct?
    a. 25%
    b. 50%
    c. 0%
    d. 25%

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    (Original post by Dadeyemi)
    Question: If you choose an answer to this question at random, what is the probability that you will be correct?
    a. 25%
    b. 50%
    c. 0%
    d. 25%

    e. mumble something vague about an ill-defined probability space and then regard the question with aloof disdain, claiming to have answered it fully and for it to be "trivial"

    Spoiler:
    Show
    Or at least that's what Grimmett taught our year
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    (Original post by Dadeyemi)
    Question: If you choose an answer to this question at random, what is the probability that you will be correct?
    a. 25%
    b. 50%
    c. 0%
    d. 25%

    I'm guessing the law of the excluded middle features quite a bit in this paradox.

    Logical bit
    Spoiler:
    Show

    Assume a and d are correct. Then you have a 50% chance of answering the question right at random. SO a and d can't be right.

    Assume b is right. Then you have a 25% chance of getting the questions right. So b is wrong

    Assume c is right. Then you have a 0% chance iof getting the answer right so c is wrong.


    Assume all the options are wrong, then you have a 0% chance of getting the answer right, so the answer is c. But then all the answers can't be wrong.


    Philosophical bit
    Spoiler:
    Show

    So both the answers "all answers are wrong" and "there is at least one correct answer" lead to contradictions. Thus the answer can be neither of them- unless we wish to change the meaning of truth to allow for (P ∧ ¬P) i.e. paradoxes or we accept that some statements are neither true nor false, i.e. we drop the law of the excluded middle: ¬(P ∧ ¬P).

    I think this questions an example of one that can only be answered only with statements whose truth leads directly to a contradiction. Let's just say that such questions are undecidable and save a lot of time ;p

    Another example of an undecidable question would be:
    The sentence below is false
    The sentence above is true
    None of these three sentences are true.

    Which sentences are true?


    Nice problem though; a shame I had to ruin it with my logical analysis.: )

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Updated: April 9, 2014
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