(1/3)*n^3, magically! hmm! But hey, it makes sense, that is a sum of all (n-x)^2, and as he assumed for all pivots it is a continues variable then the discrete sum of continues variables turns into integral and there you have it, 1/3n^3.####[['(1/3)*n^3', 'Mathematical_Related_Concept', 'POS'], ['NULL', 'Instructor', 'POS']]