A particle of mass m is located in a unidimensional potential field wher epotential energy of the particle is given by:

U(x)=A/x^2 - B/x^2

A and B are +ve constants

Find the period for small oscillations which the particle perform bout its mean position

Ans=(  A*(mA)^0.5) /B^2

i think we can find the force from

F=-(dU/dr)

then this F=ma

and the we find  and hence time period as the other one also said but on doing it i m not getting the ans

plz tell the full soln of it