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integration help(i think?)

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    1. The gradient of a curve is given by dy/dx=3x-4. Find the equation of the curve given that it passes through the point (3,1)

    so integrate 3x-4 so= 3x^2/2-4x. can i get rid of the 2 on the denominator?
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    (Original post by dongonaeatu)
    1. The gradient of a curve is given by dy/dx=3x-4. Find the equation of the curve given that it passes through the point (3,1)

    so integrate 3x-4 so= 3x^3/3-4x. can i get rid of the 3 on the denominator?
    Where are you getting the 3 from?
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    To integrate you increase the power by one and divide by the new power. So yes you can cancel the 3 and would therefore have y=x^3-4x+d

    Don't forget to include the constant!!!!

    Solve using the values you know to find d.
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    Is your original expression supposed to be dy/dx = 3x - 4, i.e. the equationn of a straight line? If you've integrated incorrectly.

    If it is supposed to be dy/dx = 3x^2 - 4, i.e. a quadratic, then yes, this gives you y = (3x^3)/3 - 4x + c. Of course you can cancel the 3s in the first term - it is just three times something divided by three.
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    Isn't it divided by two, not three :P


    You divide by the new power bro

    Also, +k on the end.
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    (Original post by CD315)
    Where are you getting the 3 from?
    sorry, i meant 2.

    is the final answer for the equation of the curve y=3x^2/2-4x-1/2
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    (Original post by tamimi)
    Isn't it divided by two, not three :P


    You divide by the new power bro

    Also, +k on the end.
    is the final answer for the equation of the curve y=3x^2/2-4x-1/2
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    That's what I make it.
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    (Original post by dongonaeatu)
    is the final answer for the equation of the curve y=3x^2/2-4x-1/2
    I believe it is Either that or we're both wrong.
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    Yep I seem to get -1/2. You don't need to get rid of the two, just sub in your x and y values after you've integrated. Best way just in case you make a mistake in getting rid of the 2.
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    (Original post by mr tim)
    Yep I seem to get -1/2. You don't need to get rid of the two, just sub in your x and y values after you've integrated. Best way just in case you make a mistake in getting rid of the 2.
    thanks tim, are you good at trigonometry?
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    (Original post by dongonaeatu)
    thanks tim, are you good at trigonometry?
    if you can tell me the question then I'll or someone else will tell you how to answer it.
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    (Original post by mr tim)
    if you can tell me the question then I'll or someone else will tell you how to answer it.
    http://www.thestudentroom.co.uk/show...260&p=37114590

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