the nth term of a sequence an^3 -2n^2 n d, where a and d are constants. The sequence has a third difference 12.
(A) if the first term of the sequence is 4,
i) find the value of a and d.
ii) write down the next four terms of the sequence.
(B) the first four terms of another sequence are 0, 7, 38, 99, 204.
i) by comparing this sequence with the one in part (a), write down, in terms of n, a formula for the nth term of the sequence.
ii) hence, find the 75th term of this sequence.