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Math Help - Help finding area of the region between x-axis and the graph.

  1. #1
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    Help finding area of the region between x-axis and the graph.

    Q: Find the total area of the region between the x-axis and the graph of y= -x^2 -3x, -8 smaller or equal to x and x smaller or equal to 2.

    Right now I'm doing cal2 and we have been using integrals to solve most problems. How can I solve this one?

    Now I think the integrals should be -8, -3 and -3, 0 and 0, 2.
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  2. #2
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    Quote Originally Posted by solidstatemath View Post
    Q: Find the total area of the region between the x-axis and the graph of y= -x^2 -3x, -8 smaller or equal to x and x smaller or equal to 2.

    Right now I'm doing cal2 and we have been using integrals to solve most problems. How can I solve this one?

    Now I think the integrals should be -8, -3 and -3, 0 and 0, 2.
    let f(x) = -x^3-3x

    \displaystyle A = -\int_{-8}^{-3} f(x) \, dx + \int_{-3}^{0} f(x) \, dx - \int_0^2 f(x) \, dx
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    Right! They must follow, how could I ignore that! Thanks man I'll post once I've solved it.
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  4. #4
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    I end up with -223/3 for the area. Since it must be the absolute value it is 223/3. What did you get?
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  5. #5
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    Quote Originally Posted by solidstatemath View Post
    I end up with -223/3 for the area. Since it must be the absolute value it is 223/3. What did you get?
    My calculator says the area = 277/3 ... don't you have a calculator to check your work?
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  6. #6
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    Yes I recalculated and got it. Must had a bad sign somewhere.
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