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Math Help - [SOLVED] Finding the gradient of a point on a curve... help please??!!

  1. #1
    Ife
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    [SOLVED] Finding the gradient of a point on a curve... help please??!!

    This is a simple enough question, well at least i assume it should be, but it's stumping me somewhat, how they've derived the answer that they put.
    can someone walk me through it? I dunno where i may be going wrong... I've been practicing similar questions with ok enough luck but this one, i dunno..
    The question reads as follows:
    Given that y=x^3 - 12x, find the slope of the curve at the point P, where P = (1, -11). (Find the gradient of the secant slope)
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    Quote Originally Posted by Ife View Post
    it's stumping me somewhat, how they've derived the answer that they put.
    What was their answer? What have you tried? Have you learned the derivative formulas yet, or are you still doing approximations with secant lines?

    Please be complete. Thank you!
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  3. #3
    Ife
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    This is a simple method, involving the change in y / the change in x, using the given point, and another point (x+h) and its corresponding y value (that would be calculated when (x+h) is substituted). I haven't done any differentiation or anything as yet...

    And their answer is -9
    Last edited by mr fantastic; September 30th 2009 at 04:18 AM. Reason: Merged posts
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  4. #4
    Ife
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    hey, i got the answer out. i was substituting something wrong. i figured it out. its quite simple. ( i knew that)
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