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Math Help - What is the derivative?

  1. #1
    Junior Member
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    Nov 2008
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    36

    What is the derivative?

    f(x)= 1/4(x^7 - x^3) at x=1

    Thanks
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  2. #2
    Newbie
    Joined
    May 2008
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    13

    Common derivative rules

    f(x)= 1/4(x^7 - x^3) at x=1

    First, we bring the constant 1/4 out front :
    \frac{1d(x^7-x^3)}{4dx}

    Then, because of the linearity of derivatives:
    \frac{1dx^7}{4dx}-\frac{1dx^3}{4dx}

    Then we apply the power rule twice, resp. for x^7 & x^3

    Thus, the undefined solution is:
    \frac{7x^6}{4}-\frac{3x^2}{4}

    Finally, we fill in x=1:
    \frac{7*1^6}{4}-\frac{3*1^2}{4}=\frac{7-3}{4}=\frac{4}{4}=1

    I recommend you to take a look at the common rules for derivatives. If you still have any problems, you can always ask them here . Have fun finding derivatives!
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