How Do I Solve Part B of the Lennard-Jones Potential Problem?

[Oblio]

I'm really stuck on b.) of this question.

http://www.physics.brocku.ca/Courses/2P20/problems/prob_lenardjones.pdf

I think I can use T = E - U, and solve for v from within T and integrate for x...

but what do I do with E?

 

[Oblio]

can i ignore E since its a constant? I got something like,
x = /frac{-6r^6A + 12B}{2r^13} t^2 [\tex]

 

[christianjb]

The minimum is the point at which dV/dr=0

 

[Oblio]

I'm getting the ridiculous value of :

r = \sqrt[6]{\frac{-12B}{6A}}

by deriving the two quotients, allowing A' and B' to cancel in the process (constants) cancelling out the high denominators as much as possible... etc..