1. The problem statement, all variables and given/known data (a) Expand (1-x6)4 (b) Find the coefficient of xr, where r is a non-negative integer, in the expansion of (1-x)-4 for |x|<1. (c) Using (a) and (b), or otherwise, find the coefficient of x^8 in the expansion of ((1-x6)/(1-x))4 for |x|<1. (Answers: (a) 1-4x6+6x12-4x18+x24 (b) (r+1)(r+2)(r+3)/6 (c) 125) 2. Relevant equations Binomial Expansion: n(n-1)...(n-r+1)*xr/r! 3. The attempt at a solution I can solve parts (a) and (b) but not part (c). I tried (-4)(2+3)(2+2)(2+1)/6 = -40 but not correct. Can anyone tell me how to solve it? Thank you very much!