Find the Interval on Which $f ( x ) = x e ^ { - x }$

question 161

Multiple Choice

Find the interval on which $f ( x ) = x e ^ { - x }$ is increasing.

• A) \(( - \infty , 1 ]\)
• B) \(( - \infty , 2 ]\)
• C) \(( - \infty , 3 ]\)
• D) \([ 1,2 ]\)
• E) \([ 1 , e ]\)
• F) \(( - \infty , e ]\)
• G) \(( - \infty , \infty )\)
• H) \(\left( - \infty , \frac { 1 } { e } \right)\)