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    June 14 FP2 paper
    Question: https://gyazo.com/7465ec0794cc7e5591ff6c1cf5c9c738
    Mark scheme: https://gyazo.com/05340a73e15953bf33df8feb2fd276b5
    My question: e^-x is part of the complementary function, so why did they not use Axe^-x as the particular integral instead? Because from what i've learnt if the particular integral occurs in the complementary function then you'll have to times by x
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    [QUOTE=Patrick2810;65461003]but what is the equation of the circle C? (after the transformation)[/QUOTE

    its (u- 9/8)^2 + v^2 = 9/64
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    (Original post by Nerrad)
    June 14 FP2 paper
    Question: https://gyazo.com/7465ec0794cc7e5591ff6c1cf5c9c738
    Mark scheme: https://gyazo.com/05340a73e15953bf33df8feb2fd276b5
    My question: e^-x is part of the complementary function, so why did they not use Axe^-x as the particular integral instead? Because from what i've learnt if the particular integral occurs in the complementary function then you'll have to times by x
    It's because in the complimentary function it doesn't have a constant in front of it. It has Acos3x or Bsin3x in front of it. If the complimentary function was of the form Ae^-x +Be^-3x then yes you test xe^-x because both the CF's and PI's e^-x have a constant in front of it and nothing else.
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    (Original post by target21859)
    It's because in the complimentary function it doesn't have a constant in front of it. It has Acos3x or Bsin3x in front of it. If the complimentary function was of the form Ae^-x +Be^-3x then yes you test xe^-x because both the CF's and PI's e^-x have a constant in front of it and nothing else.
    But why?
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    (Original post by target21859)
    It's because in the complimentary function it doesn't have a constant in front of it. It has Acos3x or Bsin3x in front of it. If the complimentary function was of the form Ae^-x +Be^-3x then yes you test xe^-x because both the CF's and PI's e^-x have a constant in front of it and nothing else.
    If you expand the bracket into A(e^-x)sin(3x) + B(e^-x)cos(3x) doesn't that makes it "have a constant in front of it" ?
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    (Original post by Nerrad)
    June 14 FP2 paper
    Question: https://gyazo.com/7465ec0794cc7e5591ff6c1cf5c9c738
    Mark scheme: https://gyazo.com/05340a73e15953bf33df8feb2fd276b5
    My question: e^-x is part of the complementary function, so why did they not use Axe^-x as the particular integral instead? Because from what i've learnt if the particular integral occurs in the complementary function then you'll have to times by x
    You can't use e^-x for the PI because it is an invalid solution. You would get 9 = 27 essentially. If you make the the PI y = ke^x you get a valid solution. ke^x wouldn't work IF it gave LHS = 0. This would be invalid because you can't have a solution that satisfies LHS = 0 and LHS = 27e^x at the same time. Only in this situation would you use
    y = kxe^-x

    (I used k as a constant)
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    (Original post by Pyslocke)
    You can't use e^-x for the PI because it is an invalid solution. You would get 9 = 27 essentially. If you make the the PI y = ke^x you get a valid solution. ke^x wouldn't work IF it gave LHS = 0. This would be invalid because you can't have a solution that satisfies LHS = 0 and LHS = 27e^x at the same time. Only in this situation would you use
    y = kxe^-x

    (I used k as a constant)
    You might wanna rephrase your answer because I don't think i understand what you're saying
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    (Original post by Nerrad)
    If you expand the bracket into A(e^-x)sin(3x) + B(e^-x)cos(3x) doesn't that makes it "have a constant in front of it" ?
    The point is that it's still being multiplied by other non-constant functions
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    (Original post by Nerrad)
    If you expand the bracket into A(e^-x)sin(3x) + B(e^-x)cos(3x) doesn't that makes it "have a constant in front of it" ?
    But it also has sin3x or cos3x attached to it. It's not Ae^-x on its own.
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    (Original post by target21859)
    But it also has sin3x or cos3x attached to it. It's not Ae^-x on its own.
    Ok thanks
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    (Original post by Nerrad)
    Ok thanks
    No problem
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    This is a bit unrelated to the thread but is there a way to remove the UCAS clearing pop-up notification? It comes up every time I refresh or click through a few pages. It's quite annoying ^^
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    (Original post by target21859)
    But it also has sin3x or cos3x attached to it. It's not Ae^-x on its own.
    Just had a thought because no matter how much you differentiate A(e^-x)sin(3x) + B(e^-x)cos(3x) it'd always be a product of 2 functions, never a function of e by itself, which was the explanation i needed...
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    (Original post by target21859)
    This is a bit unrelated to the thread but is there a way to remove the UCAS clearing pop-up notification? It comes up every time I refresh or click through a few pages. It's quite annoying ^^
    Ad block probs
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    (Original post by 13 1 20 8 42)
    Ad block probs
    Can't have it on my phone.
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    (Original post by Nerrad)
    Just had a thought because no matter how much you differentiate A(e^-x)sin(3x) + B(e^-x)cos(3x) it'd always be a product of 2 functions, never a function of e by itself, which was the explanation i needed...
    True that is a much better way of explaining it
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    stuck on fp2 june 09 question 6 where I can't get the correct circle equation, can someone have a look please!!
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    (Original post by thatapanydude)
    stuck on fp2 june 09 question 6 where I can't get the correct circle equation, can someone have a look please!!
    |-iw| = |w|

    To further explain:
    Spoiler:
    Show
    |-iw| = |-1| \times |i| \times |w|

    |-1| = 1
    |i| = 1

    \therefore |-1||i||w| = 1 \times 1 \times |w|

    \rightarrow  |w|
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    (Original post by edothero)
    |-iw| = |w|

    To further explain:
    Spoiler:
    Show
    |-iw| = |-1| \times |i| \times |w|

    |-1| = 1
    |i| = 1

    \therefore |-1||i||w| = 1 \times 1 \times |w|

    \rightarrow  |w|
    Thanks mate, I could originally see where the -1 went but not the i, but I understand it know. Thanks again!!
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    anyone have a link to the 2013 withdrawn paper, the one on pmt has a big watermark on, see https://8dedc505ac3fba908c50836f5905...%20Edexcel.pdf
 
 
 
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