Given g(x)=x2e−x
To find where the function is increasing, find where g′(x)>0.
Using the product rule with f=x2 and h=e−x:
g′(x)=(2x)(e−x)+(x2)(−e−x)
g′(x)=2xe−x−x2e−x
Factor out the common term e−x:
g′(x)=e−x(2x−x2)
g′(x)=e−x⋅x(2−x)
For the function to be increasing, g′(x)>0:
e−x⋅x(2−x)>0
Since e−x>0 for all x, the inequality reduces to:
x(2−x)>0
The critical points occur when x(2−x)=0:
x=0 or x=2
Testing the intervals:
For x<0 (test x=−1): (−1)(2−(−1))=(−1)(3)=−3<0
For 0<x<2 (test x=1): (1)(2−1)=(1)(1)=1>0
For x>2 (test x=3): (3)(2−3)=(3)(−1)=−3<0
The function g(x)=x2e−x is increasing on the interval (0,2).