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    (Original post by husband material)
    Nah,

    It would 3ln|x|

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    Okay thank you


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    (Original post by 20Emily1998)
    Is that core 3 or 4 because I'm confused by your working


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    Well you learn the differentiation of ln x in core 3, and apply it to integration in core 4
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    (Original post by 20Emily1998)
    I think so just wanted to double check as 3x^-1

    Increase power so 3x^0 divided by 0 should be nothing, I think?


    Posted from TSR Mobile
    It's a special case where the denominator differentiates to a magnitude of the numerator so 3/x x differentiates to 1
    so integral of 3/x would be 3lnx + c

    you don't need to know it for AS it's C4 shiz
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    Can someone please explain part d for me.
    JAN 2006 edexcel
    4. The first term of a geometric series is 120. The sum to infinity of the series is 480.
    (a) Show that the common ratio, r, is 3/4.
    (b) Find, to 2 decimal places, the difference between the 5th and 6th terms.
    (c) Calculate the sum of the first 7 terms.

    The sum of the first n terms of the series is greater than 300.
    (d) Calculate the smallest possible value of n.
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    Is the leak rumour true
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    (Original post by Pato1)
    Is the leak rumour true
    seriously? a leak i doubt it
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    (Original post by alishahussain832)
    Can someone please explain part d for me.
    JAN 2006 edexcel
    4.The first term of a geometric series is 120. The sum to infinity of the series is 480.
    (a)Show that the common ratio, r, is 3/4.
    (b)Find, to 2 decimal places, the difference between the 5th and 6th terms.
    (c)Calculate the sum of the first 7 terms.

    The sum of the first n terms of the series is greater than 300.
    (d)Calculate the smallest possible value of n.
    Name:  ImageUploadedByStudent Room1431794062.564739.jpg
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    Ask away if you have any questions!


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    (Original post by Medicjug)
    Name:  ImageUploadedByStudent Room1431794062.564739.jpg
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Size:  139.0 KBName:  ImageUploadedByStudent Room1431794079.337202.jpg
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    Ask away if you have any questions!


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    Thank you.
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    Can anyone help on question 3? Im not getting the correct answer for the predicted profit.

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    Hey guys, what formulas should we know for the applications of differentiation in terms of like areas and surface area etc?
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    Guys I need help, can somebody link me a video or anything for the binomial expansion where the power is n
    (2-3x)^n for example, It's never come up but I've got a good feeling it will this time
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    (Original post by Anon_98)
    Can anyone help on question 3? Im not getting the correct answer for the predicted profit.

    Posted from TSR Mobile
    Why not fam

    ar^(n-1)

    If 2013 is n=1
    Then 2016 would be n=4

    Now just plug it in :yes:

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    (Original post by husband material)
    Why not fam

    ar^(n-1)

    If 2013 is n=1
    Then 2016 would be n=4

    Now just plug it in :yes:

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    Ahhhhh- haha, thank you!

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    Can anyone help can't seem to get my head round why integrating gives you the cross sectional area and not not the whole area of the river?



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    Is it worth doing the Solomon papers or should I stick to the actual papers?
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    (Original post by Medicjug)
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    Can anyone help can't seem to get my head round why integrating gives you the cross sectional area and not not the whole area of the river?



    Posted from TSR Mobile
    Because you're only measuring the distance from point 0 to 20. The river is a lot bigger than that (I assume).
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    (Original post by fire_and_ice)
    Is it worth doing the Solomon papers or should I stick to the actual papers?
    Do solomons if you finish the actual ones


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    (Original post by Medicjug)
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    Can anyone help can't seem to get my head round why integrating gives you the cross sectional area and not not the whole area of the river?



    Posted from TSR Mobile
    What do you mean by the area of the whole river?
    The equation given describes the shape of the river bed at a single point along its length.
    When you find the area between this curve and the x axis (the surface of the river) you are by definition working out the cross sectional area of the river at that point.


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    I don't think I'm getting the right expression for L, I did cross sectional area x L but when I sub it in to get area I don't get the answer in part b
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    (Original post by studentwiz)


    I don't think I'm getting the right expression for L, I did cross sectional area x L but when I sub it in to get area I don't get the answer in part b
    What equation have you formed for volume and hence rearranged for l ?


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