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Math Help - relative min

  1. #1
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    relative min

    let f be the function given by f(x)=x^4/16-x^3+3x^2/8-2x. The function f has a relative minimum at x=
    a. 0
    b. 8
    c. 11.8
    d. 12
    e. 15.74
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  2. #2
    o_O
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    Solve for f'(x) = 0 and use your first derivative test to determine which solution represents a minimum. If you're having trouble, post what you have done and please try to use brackets.
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  3. #3
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    i did the first deriv test to get f'(x)= 1/4x^3 -3x^2 +3/4x-2
    but then when i graphed on the calc, there were no zeroes. So does this mean that it's A?
    if there are no zeroes, how can i test points to find local max's or min's?
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  4. #4
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    Try zooming out a bit more.
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  5. #5
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    Quote Originally Posted by andrewsx View Post
    i did the first deriv test to get f'(x)= 1/4x^3 -3x^2 +3/4x-2
    but then when i graphed on the calc, there were no zeroes. So does this mean that it's A?
    if there are no zeroes, how can i test points to find local max's or min's?
    That the answer is c. is clear from a graph (using a graphics calculator) of y = f(x). Note that the value of y at x = 11.8 is -402.6 ........

    I doubt you'd be expected to do this question in a technology free environment.
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