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Math Help - derivative of xe^(-x)

  1. #1
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    derivative of xe^(-x)

    When I use the product rule to find the derivative of

    xe^(-x) I get

    xe^(-x) + e^(-x) but the correct answer is y'=(1-x)e^(-x)

    which is e^(-x) - xe^(-x)

    why am I getting a plus when the answer is a minus?
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  2. #2
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    Re: derivative of xe^(-x)

    Hey kingsolomonsgrave.

    Recall that d/dx e^(-x) = -e^(-x).
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  3. #3
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    Re: derivative of xe^(-x)

    oh! thanks
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