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Math Help - Riemann Sum Help

  1. #1
    Junior Member
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    Riemann Sum Help

    Use the values 1,1.5,2,4,5 to subdivide the interval [1,5] into subintervals. Using these subintervals and the right end-points of each subinterval as the sample points, compute a Riemann sum for the integral [1,5] ∫ 2*x^2*ⅆx.


    I don't know how to to do this. I try doing it like this:
    (4/5)*(f(1)+f(1.5)+f(2)+f(4)) and I get 64.32
    The online homework system says its wrong, and I don't know any other way to do it.
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  2. #2
    Member Em Yeu Anh's Avatar
    Joined
    Nov 2009
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    94

    Red face

    How did you get (4/5) as \Delta{x}?
    The intervals are not at equal distances, you have to multiply each height by a different distance. The proper equation should be:

     (0.5*f(1.5)) + (0.5*f(2)) + (2*f(4)) + (1*f(5))

    When I solved that I had 120.25

    I hope that's the correct answer.
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