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Math Help - find the volume by rotating about x-axis

  1. #1
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    find the volume by rotating about x-axis

    use the graph to find approximate x-coordinates of the points of intersection of the given curves. then find (approximately) the volume of the solid obtained by rotating about the x-axis the region bounded by these curves

    y=x^2
    y=\sqrt{x+1}

    I tried this and got the wrong answer.
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  2. #2
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    Quote Originally Posted by yoman360 View Post
    use the graph to find approximate x-coordinates of the points of intersection of the given curves. then find (approximately) the volume of the solid obtained by rotating about the x-axis the region bounded by these curves

    y=x^2
    y=\sqrt{x+1}
    First you find the bounds.
    x^2=\sqrt{x+1} (I used a graphing calculator to find the two intersections).
    x_1=-.724492; x_2=1.2207441

    You know that area of a circle is \Pi r^2.
    Then you set up the integral.
    \Pi\int^{x_2}_{x_1} (\sqrt{x+1}^2-(x^2)^2)dx
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