a)S = 1 + 1/3 + 1/9 + 1/27 + ..................... + 1/2187
b)S = 1 + 1/2 + 1/4 + 1/8 + ..................... + 1/128 + 1/256
c)A = 1 + 2 + 4 + 8 + ..................... + 4096 + 8192
d)1/1 x2 + 1/ 2 x 3 + 1/ 3 x 4 + ................. + 1/ 2013 x 2014
h)A = 1/1 x3 + 1/ 3 x 5 + 1/ 5 x 7 + ................. + 1/ 2013 x 2015
bai2a)1/ 2 x (1 + 2) + 1/ 2 x (1 + 2 + 3) + ............ + 1/2 x (1 + 2 + 3 + ....... + 9)
ai nhanh tick đúng nha