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    Okay jan 2013 help!!!!

    Question c)

    Would like if someone can explain through worked solution preferable a picture of your working! Name:  ImageUploadedByStudent Room1371309749.205103.jpg
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    how would people integrate 1) x/x-2 and 2) x/2-x
    ?
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    I made these for C2, but they're still relevant to C4, so here are the formulas for shapes etc, and the log rules

    Sorry its a bit all over the place but hope it helps!
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    Today can we all use this thread with productive revision! No more dwelling on Thursday! Lets murk c4 by helping each other out let's crank up our revsion with the question I posted previously lol

    On a serious note need help on that question!!! Jan 13 paper look at the pic I posted earlier!!!




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    (Original post by orange94)
    Okay jan 2013 help!!!!

    Question c)

    Would like if someone can explain through worked solution preferable a picture of your working! Name:  ImageUploadedByStudent Room1371309749.205103.jpg
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    Sure let me grab some paper
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    (Original post by orange94)
    Okay jan 2013 help!!!!

    Question c)

    Would like if someone can explain through worked solution preferable a picture of your working! Name:  ImageUploadedByStudent Room1371309749.205103.jpg
Views: 169
Size:  130.0 KB


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    Here you are, sorry its a bit messy. let me know if you don't understand something
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    (Original post by nukethemaly)
    I made these for C2, but they're still relevant to C4, so here are the formulas for shapes etc, and the log rules

    Sorry its a bit all over the place but hope it helps!
    so jelly of that handwriting :zomg:
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    (Original post by justinawe)
    so jelly of that handwriting :zomg:
    I cant keep it up during exams though hahaha
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    (Original post by nukethemaly)
    I cant keep it up during exams though hahaha
    Who can? My handwriting is meh as it is... during exams it's probably illegible
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    (Original post by Econ1994)
    how would people integrate 1) x/x-2 and 2) x/2-x
    ?
    HI Im not too sure either but I think it's by substitution.

    take u = x - 2
    so that du/dx = 1 meaning du = dx
    and also note that x = u + 2

    the question can then be written as (u+2)/u so that you have to integrate 1 and (2/u)
    this gives u + 2 ln (x - 2 )

    subtitution u = x - 2 gives

    x - 2 + 2 ln (x - 2 ) + c

    ^ please check if the answer is right. If it is, use a similar method to solve part b
    Hope this helps
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    (Original post by Econ1994)
    how would people integrate 1) x/x-2 and 2) x/2-x
    ?
    Here you are!
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    (Original post by justinawe)
    Who can? My handwriting is meh as it is... during exams it's probably illegible
    I read examiner reports for biology sometimes and my god, you should see a few of the students on there. They still score full marks surprisingly. It must be tough being an examiner.
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    (Original post by Econ1994)
    how would people integrate 1) x/x-2 and 2) x/2-x
    ?
    substitution
    u=x-2 so du/dx= 1 du=dx
    x=u+2
    so u integrate u+2/u = 1+2/u
    which is u + 2ln|u|+c
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    (Original post by nukethemaly)
    I read examiner reports for biology sometimes and my god, you should see a few of the students on there. They still score full marks surprisingly. It must be tough being an examiner.
    It probably is. Some people have bad enough handwriting as it is, who knows what kinds of abominations are churned out in exams?
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    so is anyone changing their c4 prep i am im going to do less papers and more questions from the book as the book has sooooooo many questions that book was key for my m1 i think topic based studying is better for maths than just doing loads of past papers also the book questions are harder then the papers but im kind of scared of C4 the pressure was high for C3 and a little change in style distorted me i hope il keep it together for C4
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    (Original post by Econ1994)
    how would people integrate 1) x/x-2 and 2) x/2-x
    ?
    An alternate method (instead of substitution) would be to just split it into partial fractions. Which in this case would probably be simpler and faster than substitution, though both methods should be pretty quick.


    \displaystyle \int \frac{x}{x-2} \ dx

    = \displaystyle \int \frac{x-2+2}{x-2} \ dx

    = \displaystyle \int \left( \frac{x-2}{x-2} + \frac{2}{x-2} \right) \ dx

    = \displaystyle \int \left( 1 + \frac{2}{x-2} \right) \ dx

    = x + 2\ln (x-2) + C


    Noting that \dfrac{x}{2-x} = - \dfrac{x}{x-2}, you should be able to do part b the same way.
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    Hey, could someone please explain Q20 from Review exercise C4 book. I'm not sure how you would get a.b from the info given! Thanks
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    Name:  image.jpg
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    Since people are helping, might as well ask for help.

    HOW DO YOU DO (a) ?

    Thanks
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    (Original post by Econ1994)
    how would people integrate 1) x/x-2 and 2) x/2-x
    ?
    (Original post by Econ1994)
    how would people integrate 1) x/x-2 and 2) x/2-x
    ?
    In this case I firstly make the substitution of u = x-2 therefore du = dx
    So because u = x -2 then x = u + 2 so the new equation is

    u+2/u du the next step is to split the fraction into 2

    u/u + 2/u now because du = dx you can integrate with respect to x giving

    1 dx + 2/x-2 dx which = x + 2 ln [x-2] + C

    And its the same for x/2-x except it would be negative because

    x/2-x = -x/x-2
    • Welcome Squad
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    (Original post by Revisionbug)
    so is anyone changing their c4 prep i am im going to do less papers and more questions from the book as the book has sooooooo many questions that book was key for my m1 i think topic based studying is better for maths than just doing loads of past papers also the book questions are harder then the papers but im kind of scared of C4 the pressure was high for C3 and a little change in style distorted me i hope il keep it together for C4
    Yep, my C4 revision did a complete U-turn after Thurs, & yeah I'm hardly doing any past papers now but instead just like you I'm doing topic based revision so I'm completing questions from the book & looking through past papers at the same time as with C4 the questions tend to be topic based anyway in the exam but obvs the prob now is timing hence I'm really cutting corners so only practising things which look tricky which unfortunately there are a lot of esp in integration & the differential topics. Anyway I just hope that after the C3 shock we've all become immune to the fact that we could get 1 monster of a C4 paper after all, C4 is hard enough as it is. Just don't panic in the exam whatever you do, seriously & now I need to follow my own advice Good Luck!
 
 
 
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