## Calculus: Early Transcendentals (2nd Edition)

$f'(x) = \frac{1-x}{e^x}$
$f(x)=xe^{-x} = \frac{x}{e^x}$ Quotient Rule: $f'(x) = \frac{(1)(e^x)-(x)(e^x)}{e^{2x}} = \frac{e^x-xe^x}{e^{2x}} = \frac{1-x}{e^x}$