1. The problem statement, all variables and given/known data 2. Relevant equations All should be there, except taylor series, which is found here: http://mathworld.wolfram.com/TaylorSeries.html 3. The attempt at a solution For part a, I got: F(r)= [itex]\alpha[/itex](ke2)((-r0/r2)+(r0n/rn+1)) since force is the negative derivative of potential. I'm pretty sure the answer to part b will involve a taylor expansion, but I'm not sure if the f(x) I use will be the equation I found in part a, or the derivative of the equation I found in part a. Additionally, I'm not sure how, in the answer we're supposed to get that's listed in the problem, they got (n-1) and the n term in the second part out of the exponent. Thanks for any help!