The text introduction to question 2.4 gives an expression for Exp[-B*V(x)], and then guides me to use +- infinity as limits of integration.
By making the substitution r=(x-x0) the relevant integrals become much simpler, although this (or an incorrect application of this) may be my problem :/
Setting denominator D=Int[Exp[-BV(x)]]dx and expanding the Exp[-B*V(x)] as given in the question gives two integrals where I get the first to be equal to ((2*pi)/(Bk))^(1/2) and the second to be equal to 0, however it is the second integral which is multiplied by BK_3/6
The next part of the question (or the same part?) gives d
If anyone could kindly explain where I've messed this up (since my expression gives the numerator to be 0) I would very much appreciate it