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Math Help - Differentiation

  1. #1
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    Differentiation

    a wee bit stuck
    Given f(x) = 5 + 7x x^4, find f ' (x).
    Use your result to find f ' (2)
    im not sure what to do at all.
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Koops View Post
    a wee bit stuck
    Given f(x) = 5 + 7x x^4, find f ' (x).
    there is a rule you must follow:

    \frac d{dx} x^n = nx^{n - 1}

    \frac d{dx} means the derivative with respect to x

    example:
    f(x) = x^3 + 2x^2 + 3x + 1

    \Rightarrow f'(x) = 3x^2 + 4x + 3

    (did you see how the rule was applied?)


    Use your result to find f ' (2)
    im not sure what to do at all.
    just plug in x = 2 once you have found f ' (x)<br />


    can you finish?
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  3. #3
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    i knew the rule, it becomes, 7-4x^3
    but what im unclear of is what f ' (x) means, and i dont know what to do to find it.
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Koops View Post
    i knew the rule, it becomes, 7-4x^3
    but what im unclear of is what f ' (x) means, and i dont know what to do to find it.
    what?? you found it! as you found, f'(x) = 7 - 4x^3

    f'(x) denotes the "derivative of f(x)"
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  5. #5
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    oooooooooh i had a blonde moment
    so now i just plug x=2 in
    and thats the answer
    so it would be -25..
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  6. #6
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Koops View Post
    oooooooooh i had a blonde moment
    we all have them sometimes

    so now i just plug x=2 in
    and thats the answer
    so it would be -25..
    yes
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