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Math Help - graphing problems

  1. #1
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    graphing problems

    Let R be the region in the first quadrant enclosed by the graphs of y=xe^-x, x=0, x=k for k>0. The area of R, in terms of k, is

    A) -k-1/e^k
    b)k^2/2e^k
    c)k-1-e^k/e^k
    d) e^k-k-1/e^k
    e) ke^k-e^k+1
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  2. #2
    MHF Contributor Mathstud28's Avatar
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    Quote Originally Posted by sandiego234 View Post
    Let R be the region in the first quadrant enclosed by the graphs of y=xe^-x, x=0, x=k for k>0. The area of R, in terms of k, is

    A) -k-1/e^k
    b)k^2/2e^k
    c)k-1-e^k/e^k
    d) e^k-k-1/e^k
    e) ke^k-e^k+1
    \int_0^{k}xe^{-x}dx=[-xe^{-x}-e^{-x}]\bigg|_0^{k}=(-k-1)e^{-k}+1
    Last edited by Mathstud28; April 29th 2008 at 06:33 PM.
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  3. #3
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    Upon further review, I don't think this matches up with any of the answers.

    I did integration by parts ....

    Anyone? THanks you.
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  4. #4
    MHF Contributor Mathstud28's Avatar
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    Quote Originally Posted by sandiego234 View Post
    Upon further review, I don't think this matches up with any of the answers.

    I did integration by parts ....

    Anyone? THanks you.
    I am pretty sure this is the right answre Sandiego234...I did do integration by parts
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