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Math Help - Integration help please

  1. #1
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    Integration help please

    how would i intergrate these.. how do i know when to use the chain rule when i m integrating these??


    \int xe^{-x^2}

    \int e^{\frac{-y}{2}}

    \int e^{2x}
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  2. #2
    Super Member wingless's Avatar
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    Chain rule for integration? Do you mean integration by parts?

    u substitution will be sufficient for all of these.

    Quote Originally Posted by Legendsn3verdie View Post
    \int xe^{x^2}
    u = x^2
    Quote Originally Posted by Legendsn3verdie View Post
    \int e^{\frac{-y}{2}}
    u=\frac{-y}{2}
    Quote Originally Posted by Legendsn3verdie View Post
    \int e^{2x}
    u=2x

    Also, don't forget to put dx !
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  3. #3
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Legendsn3verdie View Post
    how would i intergrate these.. how do i know when to use the chain rule when i m integrating these??


    \int xe^{-x^2}~{\color{red}dx}
    substitution, u = x^2

    \int e^{\frac{-y}{2}}~{\color{red}dy}
    substitution, u = - \frac y2

    or use the rule \int e^{kx}~dx = \frac 1ke^{kx} + C for k \ne 0

    \int e^{2x}~{\color{red}dx}
    see above


    EDIT: Well, gee, thanks a lot Wingless!
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