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    When working out if a point is a max min or point of inflection, and the answer for the second diverative is 0 then you use the 3rd deverative and its still zero what kind of point is it??


    thanks for the help in advance
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    (Original post by Superbubbles)
    When working out if a point is a max min or point of inflection, and the answer for the second diverative is 0 then you use the 3rd deverative and its still zero what kind of point is it??


    thanks for the help in advance
    If the third derivative is 0, we can't make any conclusions about the kind of point it is.

    Could you post the question you're doing?
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    find the stationary points and their nature of the equation 12x^5+5x^6+1
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    y=5x^6+12x^5+1

    y'=30x^5+60x^4

    y''=150x^4+240x^3

    at a local maximum, y' = 0 and y'' is negative
    at a local minimum, y' = 0 and y'' is positive

    30x^5+60x^4 = 0 when x = -2 or x = 0
    at x = -2, y'' = about 500 so it is a local minimum
    at x = 0, y'' = 0 so it seems to be a point of inflection
    go back to original curve to check what is going on at x=0
    at x=0, you have the middle of a very drawn-out point of inflection, since at x=-1 the gradient is positive and at x=1 gradient is also positive

    conclusion
    x=-2 is local minimum
    x=0 is point of inflection
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    (Original post by notathuggee)
    y=5x^6+12x^5+1

    y'=30x^5+60x^4

    y''=150x^4+240x^3

    at a local maximum, y' = 0 and y'' is negative
    at a local minimum, y' = 0 and y'' is positive
    Please don't post full solutions - it's against the rules of the forum

    (We try to stick to giving hints and advice so that posters can work things out for themselves.)
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    Oh damn, didn't know that.
    Sorry
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    (Original post by davros)
    Please don't post full solutions - it's against the rules of the forum

    (We try to stick to giving hints and advice so that posters can work things out for themselves.)
    Since when as this been a thing? Just asking as every thread gives full solutions. Sorry for not knowing if this is the case.
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    (Original post by Jai Sandhu)
    Since when as this been a thing? Just asking as every thread gives full solutions. Sorry for not knowing if this is the case.
    Giving full solutions is usually a last resort:

    http://www.thestudentroom.co.uk/showthread.php?t=403989

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    (Original post by Superbubbles)
    find the stationary points and their nature of the equation 12x^5+5x^6+1
    the answer is your mums pussy
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    (Original post by lizard54142)
    Giving full solutions is usually a last resort:

    http://www.thestudentroom.co.uk/showthread.php?t=403989

    Ah ok, thanks, did this anyway but was curious as I had never heard it mentioned before. Btw are other peoples notifications broken aswell?
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    (Original post by Jai Sandhu)
    Ah ok, thanks, did this anyway but was curious as I had never heard it mentioned before. Btw are other peoples notifications broken aswell?
    Yep, I haven't gotten any quote notifications since yesterday morning.
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    Even though there's a little bit of info about them in the textbook, points of inflexions are not part of the edexcel c2 syllabus

    Theres a reason why they've never come up :yes:
    Posted from TSR Mobile
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    (Original post by Jai Sandhu)
    Ah ok, thanks, did this anyway but was curious as I had never heard it mentioned before. Btw are other peoples notifications broken aswell?
    (Original post by rayquaza17)
    Yep, I haven't gotten any quote notifications since yesterday morning.
    Not just me then. I've been getting "rep" notifications but no quote notifications
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    thank you so much! It isn't a rule so thanks for the help much appreciated


    (Original post by notathuggee)
    y=5x^6+12x^5+1

    y'=30x^5+60x^4

    y''=150x^4+240x^3

    at a local maximum, y' = 0 and y'' is negative
    at a local minimum, y' = 0 and y'' is positive

    30x^5+60x^4 = 0 when x = -2 or x = 0
    at x = -2, y'' = about 500 so it is a local minimum
    at x = 0, y'' = 0 so it seems to be a point of inflection
    go back to original curve to check what is going on at x=0
    at x=0, you have the middle of a very drawn-out point of inflection, since at x=-1 the gradient is positive and at x=1 gradient is also positive

    conclusion
    x=-2 is local minimum
    x=0 is point of inflection
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    (Original post by Superbubbles)
    When working out if a point is a max min or point of inflection, and the answer for the second diverative is 0 then you use the 3rd deverative and its still zero what kind of point is it??


    thanks for the help in advance
    use the first differential method if your second derivative is 0
    examsolutions made a video on this
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    [QUOTE=yasmin#2;55928235]use the first differential method if your second derivative is 0
    examsolutions made a video on this [/QUOTE


    Thank you! The video help me so much 😊
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    [QUOTE=Superbubbles;55948191]
    (Original post by yasmin#2)
    use the first differential method if your second derivative is 0
    examsolutions made a video on this [/QUOTE


    Thank you! The video help me so much 😊
    youre welcome! good luck for your exam
 
 
 
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