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A levels maths hopefully a simple easy question Watch

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    Could someone tell me why isn't the last part x d2y/dx2 dy/dx ?
    Isn't the differential of dy/dx = d2y/dx2?
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    (Original post by maxintos)


    Could someone tell me why isn't the last part x d2y/dx2 dy/dx ?
    Isn't the differential of dy/dx = d2y/dx2?
    Yes it is. Why do you think you need to multiply it by dy/dx? You're just using the product rule here - if z = vw then z' = v'w + vw'. In this case, put v = x and w = dy/dx and it should become clearer.
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    (Original post by maxintos)


    Could someone tell me why isn't the last part x d2y/dx2 dy/dx ?
    Isn't the differential of dy/dx = d2y/dx2?
    Use the product rule on x.dy/dx and you'll see
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    (Original post by maxintos)


    Could someone tell me why isn't the last part x d2y/dx2 dy/dx ?
    Isn't the differential of dy/dx = d2y/dx2?
    I swear you cant differentiate with that method with respect to 3 variables....
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    (Original post by davros)
    Yes it is. Why do you think you need to multiply it by dy/dx? You're just using the product rule here - if z = vw then z' = v'w + vw'. In this case, put v = x and w = dy/dx and it should become clearer.
    For some reason I was stuck thinking that you have to use implicit differentiation on dy/dx like you had when differentiating y with respect to x.
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    (Original post by maxintos)
    For some reason I was stuck thinking that you have to use implicit differentiation on dy/dx like you had when differentiating y with respect to x.
    So are you happy that you understand how they got the result now?
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    (Original post by davros)
    So are you happy that you understand how they got the result now?
    Yes, with clear head everything makes much more sense.
 
 
 
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