Tính tổng sau B = 1/1.2.3.4 + 1/2.3.4.5 + 1/3.4.5.6 +...+ 1/27.28.29.30
Giải thích
B=11.2.3.4+12.3.4.5+13.4.5.6+...+127.28.29.30=1311.2.3−12.3.4+12.3.4−13.4.5+...+127.28.29−128.29.30=1311.2.3−128.29.30=13538120
B=11.2.3.4+12.3.4.5+13.4.5.6+...+127.28.29.30=1311.2.3−12.3.4+12.3.4−13.4.5+...+127.28.29−128.29.30=1311.2.3−128.29.30=13538120