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Find dy/dx at x = 2, if y =6u^2-11 and u = 3x^2 +2

  1. Apr 15, 2012 #1
    the only part im confused about is if i derive
    y = 6u^2-11 first, then substitute u with 3x^2 +2.
    or if i substitute u with 3x^2 +2, then expand/simplify, then derivate the entire question.

    i got two answers.
    using the first method f'(2) = 2016

    and the second method f'(2) = 144

    which method is right?

    or am i just completely wrong.
  2. jcsd
  3. Apr 16, 2012 #2
    2nd method is correct and its answer is 2016
  4. Apr 16, 2012 #3
    alright, thx for the clarification
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