# How do you determine the interval(s) where the function #f(x) = xe^-x# is concave down?

##### 1 Answer

Apr 30, 2015

A function is concave down in the intervals in which its second derivative is negative.

So:

(this is because the exponential function is always positive)

It's clear also seeing the graph:

graph{xe^-x [-10, 10, -5, 5]}

The point