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    (Original post by economicss)
    Please could you post a pic or link to the distance from the focus and directrix formula, not sure I've come across it, thanks
    There is this one.

    Also this:

    Focus:  (a, 0) , Directrix:  x = -a , General point:  (at^2, 2at)

    Distance from general point to focus:

     S^2 = (at^2 - a)^2 + (2at)^2 = a^2 (t^4 + 2t^2 + 1) = a^2 (t^2 + 1) \implies S = a(1+t^2)

    Distance from general point to directrix:

     D = a + at^2 = a(1+t^2)

     \therefore S = D
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    (Original post by NotNotBatman)
    What about r then?
    r is also positive it says
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    (Original post by Pyslocke)
    r is also positive it says
    oops, didn't read the question properly.
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    (Original post by SLamb)
    For proof's by induction, when the question asks to prove that _____ is divisible by X, are we allowed to use the general rule that (M^n -1) is always divisible by (M-1)? I've done that in a couple of recent assessments and been marked correct but i thought I'd be better safe than sorry
    You can factorise like this

     a^n - b^n = (a - b)( a^{n-1} + a^{n-2}b + ... ab^{n-2} + b^{n-1} )

    There is also this one:

     a^n + b^n = (a + b)( a^{n-1} - a^{n-2}b + ... )
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    (Original post by oinkk)
    Ah, that's quite handy. I'm guessing that would work for any angle of rotation.
    Yup, if the angle is less than 180, you don't need to subtract, but if it's greater than 180 you will
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    (Original post by Genius123456)
    Try this hard question and reply by sending the solution if you solve it. The hardest one you can get. I could not solve it
    Thanks in advance
    Name:  IMG_0371.jpg
Views: 220
Size:  503.3 KB

    There you go mate, i hope you can see what i wrote. By the way, which paper is that?
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    (Original post by Louisb19)
    You can factorise like this

     a^n - b^n = (a - b)( a^{n-1} + a^{n-2}b + ... + b^{n-1} )
    Ahhhhhh, that explains it for me aha, thanks!
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    Hope this helps:

    https://gyazo.com/2ee29fccfbcb4d0663d07939320ad106
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    (Original post by SLamb)
    Ahhhhhh, that explains it for me aha, thanks!
    Its the method that I used for Jan 2014 IAL 10 ii).

    Their +- way was cool too though.
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    how would i do part b
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    (Original post by iMacJack)
    Attachment 534379

    hey I can't seem to get this proof right, please give some assistance Zacken or anyone!!


    Posted from TSR Mobile
    Hope this helps:

    https://gyazo.com/2ee29fccfbcb4d0663d07939320ad106

    You can do pretty much all of the "prove f(n) is divisible by x" questions like this, by getting expressions for f(k) and f(k+1), then getting an expression for f(k+1) in terms of f(k). Since you've already assumed f(k) is divisible by "x", the rest of the expression should just work itself out.
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    Guys, do the international papers include anything that the normal ones don't?
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    (Original post by BRBBIT)
    Guys, do the international papers include anything that the normal ones don't?
    Roots of polynomials with the alpha, beta stuff is in the international paper but isn't on the UK spec.
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    Please could anyone explain how to do question 9c on here http://www.thestudentroom.co.uk/atta...9&d=1244566570 as the mark scheme doesn't show a method, thanks
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    (Original post by Chirstos Ioannou)
    Name:  IMG_0371.jpg
Views: 220
Size:  503.3 KB

    There you go mate, i hope you can see what i wrote. By the way, which paper is that?
    Smart smart smart... Cheers for that.
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    (Original post by Louisb19)
    There is this one.

    Also this:

    Focus:  (a, 0) , Directrix:  x = -a , General point:  (at^2, 2at)

    Distance from general point to focus:

     S^2 = (at^2 - a)^2 + (2at)^2 = a^2 (t^4 + 2t^2 + 1) = a^2 (t^2 + 1) \implies S = a(1+t^2)

    Distance from general point to directrix:

     D = a + at^2 = a(1+t^2)

     \therefore S = D
    Thanks so much
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    (Original post by Yua)


    how would i do part b
    Once you've worked out the angle in part a) (should be 225?) You can then do 360 / (225-180) = 8, so n=8
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    Has anyone got any hard(er than usual) FP1 questions/ papers? I have done all the papers including IAL and the textbook review exercises and am struggling to find revision material...
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    That question is from the old FP1 spec; it includes 'e', which is introduced in C3 whilst the new FP1 spec only assumes C1,C2 knowledge. You therefore don't need to be able to do it.

    (Original post by economicss)
    Please could anyone explain how to do question 9c on here http://www.thestudentroom.co.uk/atta...9&d=1244566570 as the mark scheme doesn't show a method, thanks
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    (Original post by economicss)
    Please could anyone explain how to do question 9c on here http://www.thestudentroom.co.uk/atta...9&d=1244566570 as the mark scheme doesn't show a method, thanks
    Would it not just be the answer you get for part b), multiplied by 60, and rounded to the nearest integer?
 
 
 
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