Conservative force, kinetic energy

[nothingatall]

Homework Statement

A single conservative force F(x) acts on a 2.4 kg particle that moves along an x axis. The potential energy U(x) associated with F(x) is given by
U(x) = -4xe-x/4
where x is in meters. At x = 5.0 m the particle has a kinetic energy of 5.2 J. (a) What is the mechanical energy of the system? (b) What is the maximum kinetic energy of the particle and (c) the value of x at which it occurs?

Homework Equations

Emech=K+U

The Attempt at a Solution

I know how to find the mechanical energy, but I don't know how to do the derivative of U(x) so that I can do b) and c) even though its simple.

 

[willem2]

this should be enough to find it

the derivative of e^x is e^x
the derivative of f(x)g(x) = f'(x)g(x) + f(x)g'(x)
the derivative of f(g(x)) = g'(x) f'(g(x))