assume that 1^k + 2^k + ... +n^k is a polynomial of degree k+1 in n

i.e. 1^k + 2^k +... +n^k = an^(k+1) +bn^k +cn^(k-1) + ...

what can you say about the coefficients of this polynomial? try to determine them as completely as possible

I need help with this! I can see that they will always add up to 1 (take n = 1) and obviously you could create a bunch of equations and solve them for specific n and k, but what else is there?