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    Q13

    I found dy/dx= (-3y-2x) / (3x-2y)

    I subbed in (1,1) and got dy/dx = -5 which is correct.

    Now I need to find d2y/dx2, I got (22y-18x) / (3x-2y).

    When I subbed in (1,1) I got 4, but the answer is 78

    Dunno where I went wrong?
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    My working to get d^2y/dx^x.

    I don't think that's clear enough.
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    (Original post by Vorsah)
    Q13
    Would you mind posting the whole question as it appears in the textbook?

    (Original post by Vorsah)
    My working to get d^2y/dx^x.

    I don't think that's clear enough.
    It really isn't clear enough to make out most parts.
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    (Original post by Vorsah)
    Q13

    I found dy/dx= (-3y-2x) / (3x-2y)

    I subbed in (1,1) and got dy/dx = -5 which is correct.

    Now I need to find d2y/dx2, I got (22y-18x) / (3x-2y).

    When I subbed in (1,1) I got 4, but the answer is 78

    Dunno where I went wrong?
    Rearrange to get  (3x-2y)\frac{dy}{dx}+3y+2x=0 then differentiate being very careful with the product rule and implicit differentiation and the answer comes out to 78 as required.
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    (Original post by brianeverit)
    Rearrange to get  (3x-2y)\frac{dy}{dx}+3y+2x=0 then differentiate being very careful with the product rule and implicit differentiation and the answer comes out to 78 as required.
    I got the correct answer, but I need help with this it looks simple but I'm sure which one is correct:

    Ignore this it's the wrong one.
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    (Original post by brianeverit)
    Rearrange to get  (3x-2y)\frac{dy}{dx}+3y+2x=0 then differentiate being very careful with the product rule and implicit differentiation and the answer comes out to 78 as required.
    Is it 1 or 2?
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    (Original post by Vorsah)
    Is it 1 or 2?
    Neither is correct
    Assuming I* have read waht you have written correctly
     2-\frac{18y-12x}{3x-2y}=0 \Rightarrow 2=\frac{18y-12x}{3x-2y}
 
 
 
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