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    Anyone do FP2?
    Attachment 206918
    What I attempted so far:
    Differentated with respect to t to get dy/dt=-2x^-3(dx/dt)
    Then I differentiated again to get d2y/dt2=6x^-4(dx/dt) -2x^-3(d2x/dt2)
    Then rearranged the subjects so I could sub back into the original equation~got stuck along the way though and I'm not anywhere close to the proof :O
    We got given the CD to help with revision over Easter but I can't seem to work out how to open solution bank on my laptop :/
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    I would love to help but there is a problem with the link.
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    (Original post by Gray Wolf)
    I would love to help but there is a problem with the link.
    Oh did it not attach
    Name:  FP2 31.png
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Size:  10.5 KB
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    (Original post by the.cookie.monster)
    Oh did it not attach
    Name:  FP2 31.png
Views: 158
Size:  10.5 KB
    You've done the tricky bit right. Now it comes down to this: how solid is your algebra?
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    (Original post by Indeterminate)
    You've done the tricky bit right. Now it comes down to this: how solid is your algebra?
    Okay, well when I rearranged I got:
    dx/dt=-0.5x^3(dy/dt)
    d2x/dt2=-0.5x^3(d2y/dt2)+3x^-1(dx/dt)
    Subbing in I get:
    -x^4(d2y/dt2)+6(dx/dt)-6(-0.5x^3(dy/dt))^2=x^2-3x^4
    I don't see how I would be able to get rid of (dy/dt)^2
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    (Original post by the.cookie.monster)
    Okay, well when I rearranged I got:
    dx/dt=-0.5x^3(dy/dt)
    d2x/dt2=-0.5x^3(d2y/dt2)+3x^-1(dx/dt)
    Subbing in I get:
    -x^4(d2y/dt2)+6(dx/dt)-6(-0.5x^3(dy/dt))^2=x^2-3x^4
    I don't see how I would be able to get rid of (dy/dt)^2


    \frac{d^2 y}{dt^2} = 6x^{-4}(-0.5x^3 \frac{dy}{dt}) -2x^{-3} \frac{d^2 x}{dt^2}
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    (Original post by Indeterminate)
    \frac{d^2 y}{dt^2} = 6x^{-4}(-0.5x^3 \frac{dy}{dt}) -2x^{-3} \frac{d^2 x}{dt^2}
    I've realised what I did wrong now-I differentiated incorrectly d2y/dt2
    I was supposed to get 6x^-4(dx/dt)^2 -2x^-3(d2x/dt2)
    but thanks anyway
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    (Original post by the.cookie.monster)
    I've realised what I did wrong now-I differentiated incorrectly d2y/dt2
    I was supposed to get 6x^-4(dx/dt)^2 -2x^-3(d2x/dt2)
    but thanks anyway
    Was about to say that as I was doing the Q from scratch. You were too quick

    By the way, my last post refers to the fact that

    d2x/dt2=-0.5x^3(d2y/dt2)+3x^-1(dx/dt)

    was an incorrect deduction from the wrong differentiation
 
 
 
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