Are there constants a, B, C such that (1 / N) ^ 3 + (2 / N) ^ 3 + +(n / N) ^ 3 = (an ^ 2 + BN + C) / N holds for all n belonging to n *, find out the value of a, B, C and prove it

Are there constants a, B, C such that (1 / N) ^ 3 + (2 / N) ^ 3 + +(n / N) ^ 3 = (an ^ 2 + BN + C) / N holds for all n belonging to n *, find out the value of a, B, C and prove it

Because 1 ^ 3 + 2 ^ 3 +... + n ^ 3 = [n * (n + 1) / 2] ^ 2 (which can be proved by mathematical induction), so
(1/N)^3+(2/N)^3+…… +(n / N) ^ 3 = [n * (n + 1) / 2] ^ 2 / N ^ 3 = 1 / 4 * (n ^ 4 + 2n ^ 3 + n ^ 2) / N ^ 3 = (1 / 4 * n ^ 2 + 1 / 2 * n + 1 / 4) / N, that is, a = 1 / 4, B = 1 / 2, C = 1 / 4