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    I need help with this question. It's from the OCR C4 specimen paper

    For the curve 2x² + xy + y² = 14 find dy/dx in terms of x and y

    Any help much appreciated

    Chris
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    (Original post by needmathshelp)
    I need help with this question. It's from the OCR C4 specimen paper

    For the curve 2x² + xy + y² = 14 find dy/dx in terms of x and y

    Any help much appreciated

    Chris
    This is implicit differentiation - which gives

    4x + y + xy' + 2yy' = 0

    Solving for y'

    y' = (-4x-y)/(x+2y)
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    (Original post by needmathshelp)
    I need help with this question. It's from the OCR C4 specimen paper

    For the curve 2x² + xy + y² = 14 find dy/dx in terms of x and y

    Any help much appreciated

    Chris
    [4x]+[x(dy/dx)+y]+[2y(dy/dx)]=0
    4x+x(dy/dx)+y+2y(dy/dx)=0
    (dy/dx)(x+2y)+4x+y=0
    (dy/dx)(x+2y)=-(4x+y)
    (dy/dx)=-(4x+y)/(x+2y)
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    sorted. We differentiate implicitly with respect to x.

    We must differentiate xy as a product because y is a function of x.

    2x² + xy + y² = 14

    4x + x(dy/dx) + y +2y(dy/dx) = 0

    And then rearrange...

    If you don't know why it comes out as it does then ask again.
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    Thanks

    It's all clear now
 
 
 
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