Finding Force From Potential Energy

1. The problem statement, all variables and given/known data
The potential energy of two neutral molecules may be modelled using the Lennard Jones potential,
[tex]U(x)=U_0(\frac{\sigma^{12}}{x^{12}} - \frac{\sigma^6}{x^6})[/tex]
where [itex]U_0[/itex] and [itex]\sigma[/itex] are positive constants and [itex]x[/itex] is the distance between the two molecules.

a) Find the force at an arbitrary point x ?

2. Relevant equations

conservative forces and potential energy

3. The attempt at a solution
[tex]F(x) = -\frac{dU}{dx}= U_0(12\frac{\sigma^{12}}{x^{13}} - 6\frac{\sigma^6}{x^7})[/tex]

Is my answer correct ?