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Math Help - Derivate question

  1. #1
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    Derivate questions

    Hi everyone i spent almost two hours on on these two questions that i can't answer. Please Help meee!!!!

    1)
    Given

    (a) 0
    (b) 5
    (c) - 5

    All the answers MUST be points:

    Thank you
    Last edited by mr fantastic; October 16th 2011 at 11:29 AM. Reason: Deleted question that was added after getting replies.
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  2. #2
    MHF Contributor Siron's Avatar
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    Re: Derivate question

    First of all, calculate f'(x). How can you use this to find the answers?
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  3. #3
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    Re: Derivate question

    Quote Originally Posted by danicloud View Post
    Hi everyone i spent almost two hours on this question that i can't answer. Please Help meee!!!!

    Given at which point will the curve have slope:

    (a) 0
    (b) 5
    (c) - 5

    All the answers MUST be points:

    Thank you
    Solve f'(x) = 0.

    Solve f'(x) = 5.

    Solve f'(x) = -5.

    I hope you understand that f'(x) is the derivative of f(x) with respect to x. Remember to get the y-coordinate after you have found the value of x (use y = f(x)).

    If you need more help, please show all your work and say where you're stuck.
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  4. #4
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    Re: Derivate question

    Thank you i got that but i am still stuck.

    I found that the derivate is 12x-30. When i set it equal to 0 i get 5/2, which i substitute for x and get -73/2. Same thing for 5 and -5. However is still gives me a error
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  5. #5
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    Re: Derivate question

    Quote Originally Posted by danicloud View Post
    Thank you i got that but i am still stuck.

    I found that the derivate is 12x-30. When i set it equal to 0 i get 5/2, which i substitute for x and get -73/2. Same thing for 5 and -5. However is still gives me a error
    Your first answer is correct: (5/2, -73/2).

    However, you have not shown any working for the other two parts so it's impossible to know what your trouble is. My previous reply said to show ALL working.
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  6. #6
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    Re: Derivate question

    sorry so for 5 i found it to be: (12/35,-10511/1225) while for -5: (25/12,-851/24).

    The website marks the answer as wrong
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  7. #7
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    Re: Derivate question

    Quote Originally Posted by danicloud View Post
    sorry so for 5 i found it to be: (12/35,-10511/1225) while for -5: (25/12,-851/24).

    The website marks the answer as wrong
    Your values for x are wrong. Type out every step you did in finding them (you will most likely see your error during the process - same error for both, by the way).
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