Differentiate the funciton
H(x) = (x + x^-1)^3
Either multiply it out and differentiate is term by term, or use the function of a function "chain" rule. The first method is easier.
(x + 1/x)^2 = x^2 + 2 + 1/x^2
(x + 1/x)^3 = x^3 + 2x + 1/x + x + 2/x + 1/x^3
= x^3 + 3x + 3/x + 1/x^3
Now differentiate that. For further help from me, you will need to show your work.