2. Find the sum of the series n(n+ 1) 2 , 6 , 12 n=1 by partial fractions; examine the partial sums Sn of the series method a) Express+ method b) Sketch the curves y for 0 x 1 and n = 0, 1, 2, 3, 4 on a common plot; let An be the area between y = xn and y-Xn+1 for any n > 0; compute An in terms of n; express the area of the unit square in terms of the An; deduce the sum of the series.