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Math Help - integration

  1. #1
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    integration

    Hi I'm having trouble with integration, can someone please help me integrate this:

    <br />
\int_0^\infty e^{-\frac{x}{y}} dx <br />
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  2. #2
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    Quote Originally Posted by Pengu View Post
    Hi I'm having trouble with integration, can someone please help me integrate this:

    <br />
\int_0^\infty e^{-\frac{x}{y}} dx <br />
    It's an improper integral so the first step is:  \lim_{\alpha \rightarrow + \infty} \int_0^\alpha e^{-\frac{x}{y}} dx .

    If you need more help please show all your working and say where you're stuck.
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  3. #3
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    1. Integral of e^{-x/y} function is -y*e^{-x/y} + C.
    2. -y*e^{-x/y} -> 0 when x -> +inf

    Then the answer is y
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  4. #4
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    Quote Originally Posted by ialbrekht View Post
    1. Integral of e^{-x/y} function is

    -y*e^{-x/y} + C.

    2. -y*e^{-x/y} -> 0 when x -> +inf

    Then the answer is y
    Not clear enough (or may-be just wrong) , what happens if y<0?? Also what happens when y>0??

    CB
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  5. #5
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    i was about to say that but i forgot.

    calculations are valid for positive values. (The integrand is a positive function, it's impossible to get a negative number.)
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