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Math Help - Clarification please

  1. #1
    Junior Member NAPA55's Avatar
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    Clarification please

    I don't understand how the first question (above the line) is correct, while the second one is not and it should be the solution on the right.

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  2. #2
    Moo
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    Hi,

    The first one is correct, because when you differentiate (x+1), you got 1, whereas when you got to differentiate (3x^3), you have 9x, which should appear in f '(x).

    (u^n(x))' = u'(x).n.u^{n-1}(x)
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  3. #3
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    Because you have a composite function and you didn't use the chain rule. either use the chain rule for the second question or using the rules of indices.
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  4. #4
    Junior Member NAPA55's Avatar
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    Quote Originally Posted by bobak View Post
    Because you have a composite function and you didn't use the chain rule. either use the chain rule for the second question or using the rules of indices.
    We haven't learned any of those yet! Only power, product, and quotient rules!!
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  5. #5
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by NAPA55 View Post
    We haven't learned any of those yet! Only power, product, and quotient rules!!
    well, in that case, you should have went for the "And it should be this:" method
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