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    x= t^2 -2t

    y= t^4- 4t

    The answer is 2 ( t^2+ t+1) How???
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    (Original post by APersonYo)
    x= t^2 -2t

    y= t^4- 4t

    The answer is 2 ( t^2+ t+1) How???
    What did you get when you tried it? Please post your working.
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    (Original post by notnek)
    What did you get when you tried it? Please post your working.
    x= t^2 -2t

    dx/dt= 2t-2

    therefore dt/dx= 1/ (2t-2)

    y= t^4- 4t

    dy/dt= 4t^3 -4

    threfore dy/dx= 4t^3-4/ 2t-2


    And my answer is wrong lol
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    (Original post by APersonYo)
    x= t^2 -2t

    dx/dt= 2t-2

    therefore dt/dx= 1/ (2t-2)

    y= t^4- 4t

    dy/dt= 4t^3 -4

    threfore dy/dx= 4t^3-4/ 2t-2


    And my answer is wrong lol
    Your answer is correct but you can simplify.

    Either factorise t^3-1 or if you can't do that then you could use long division to divide the denominator into the numerator.
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    (Original post by APersonYo)
    x= t^2 -2t

    dx/dt= 2t-2

    therefore dt/dx= 1/ (2t-2)

    y= t^4- 4t

    dy/dt= 4t^3 -4

    threfore dy/dx= 4t^3-4/ 2t-2


    And my answer is wrong lol
    not wrong, just unfinished:

    4t^3-4 / 2t-2 = 4(t^3-1)/2(t-1)
    = 2(t^3-1)/(t-1)
    = 2(t-1)(t^2+t+1)/(t-1)
    = 2(t^2+t+1)
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    (Original post by APersonYo)
    x= t^2 -2t

    dx/dt= 2t-2

    therefore dt/dx= 1/ (2t-2)

    y= t^4- 4t

    dy/dt= 4t^3 -4

    threfore dy/dx= 4t^3-4/ 2t-2


    And my answer is wrong lol
    Do a polynomial division of your numerator by your denominator
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    (Original post by harrycompsci)
    not wrong, just unfinished:

    4t^3-4 / 2t-2 = 4(t^3-1)/2(t-1)
    = 2(t^3-1)/(t-1)
    = 2(t-1)(t^2+t+1)/(t-1)
    = 2(t^2+t+1)
    Thank you.

    I also have another question:

    x= cos t

    y= t(4-sint)


    I got dt/dx = 1/ -sin t

    dy/dt= 4-tcos t

    dy/dx= 4-tcos t / -sin t

    The answer is dy/ dx= t cost t - 4 cosec t +1

    How???
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    (Original post by APersonYo)
    Thank you.

    I also have another question:

    x= cos t

    y= t(4-sint)


    I got dt/dx = 1/ -sin t

    dy/dt= 4-tcos t

    dy/dx= 4-tcos t / -sin t

    The answer is dy/ dx= t cost t - 4 cosec t +1

    How???
    I think your dy/dt term is incorrect. try the product rule again
    • Thread Starter
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    (Original post by ewanwest)
    i think your dy/dt term is incorrect. Try the product rule again
    thank you so much!!!
 
 
 
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