Where is the second derivative of y = 4xex equal to 0?

Question

Question options:

1)	-4
2)	-2
3)	-1
4)	0

Answer 1

Use the product rule to start.

u'v+v'u

u = 4x

u' = 4

v = e^x

v' = e^x

this gives (4e^x + 4xe^x)

the derivative of this (product rule on 2nd part) gives

4e^x + 4e^x + 4xe^x

substituting -2 for x gives

4e^-2 + 4e^-2 +4(-2)e^-2

= 8e^-2 + (-8)e^-2

=0

answer is -2