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Math Help - Find the volume of the solid formed by rotating the region..

  1. #1
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    Find the volume of the solid formed by rotating the region..

    Hello,

    I need help with this question that i've been trying to solve for 15-20 mins and keep getting the wrong answer.

    Find the volume formed by rotating the region enclosed by:

    y=e^3x+5
    y=0
    x=0
    x= 0.4

    about the x-axis

    Can anyone show me the steps on how to solve it so I can see what mistakes i'm doing? Thank you.
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  2. #2
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    try graphing each of the functions and lines you were given
    and see what sector lies between them and use the formula for volume of solids with the right intervals.
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  3. #3
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    Quote Originally Posted by abilitiesz View Post
    Hello,

    I need help with this question that i've been trying to solve for 15-20 mins and keep getting the wrong answer.

    Find the volume formed by rotating the region enclosed by:

    y=e^3x+5
    y=0
    x=0
    x= 0.4

    about the x-axis

    Can anyone show me the steps on how to solve it so I can see what mistakes i'm doing? Thank you.
    Calculate pi*y^2, and integrate it from 0 to .4.
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  4. #4
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    Quote Originally Posted by rn443 View Post
    Calculate pi*y^2, and integrate it from 0 to .4.
    Do I plug in e^3x +5 and square it? Then get the dy of it?
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  5. #5
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    Quote Originally Posted by abilitiesz View Post
    Do I plug in e^3x +5 and square it? Then get the dy of it?
    Yes, times pi.
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  6. #6
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    Quote Originally Posted by rn443 View Post
    Yes, times pi.
    Ohh ok. I'll try it now. Thank you
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  7. #7
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    I still can't seem to get it. I think i'm doing something arithmetically wrong when plugging it in. Can someone show me how you do it so I can check what i'm doing wrong? Thank you.

    I got 72.15042729. But, it says i'm still wrong. Can anyone show me how to do it properly?
    Last edited by mr fantastic; October 23rd 2009 at 03:42 AM. Reason: Merged posts
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  8. #8
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    Quote Originally Posted by abilitiesz View Post
    I still can't seem to get it. I think i'm doing something arithmetically wrong when plugging it in. Can someone show me how you do it so I can check what i'm doing wrong? Thank you.

    I got 72.15042729. But, it says i'm still wrong. Can anyone show me how to do it properly?
    Please show all your working so that it can be reviewed.
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