The process of adding rational functions (ratios of polynomials) by placing them over a common denominator is the analogue of adding rational numbers. The reverse process of taking a rational function apart by writing it as a sum of simpler rational functions is useful in several areas of mathematics; for example, it arises in calculus when we need to integrate a rational function and in discrete mathematics when we use generating functions to solve recurrence relations. The decomposition of a rational function as a sum of partial fractions leads to a system of linear equations. Find the partial fraction decomposition of the given form.

Assuming that 1² + 2² +.......+ n = an² + bn + c, Find a, b, and c by substituting three values for n and thereby obtaining a system of linear equations in a, b, and c.