1.2.3+3.4.5+5.6.7+....+17.18.19
1.2.3+2.3.4+3.4.5+...+17.18.19+18.19.20
chứng minh A=1/1.2.3+1/2.3.4+1/3.4.5+...+1/17.18.19>1/4
1.2.3+3.4.5+5.6.7+.........+99.100.101
Tính : a, 1.2.3 + 2.3.4 + 3.4.5 + ... + (n - 1).n.(n+1)
b, 1.2.3 + 3.4.5 + 5.6.7 + 98.99.100
A = 1.2.3 + 2.3.4 + 3.4.5 + ......................+ 17.18.19
tính ???? tau ko hỏi mấy đứa lớp 6c cxh
1.2.3 + 2.3.4 + 3.4.5 + 4.5.6 + 5.6.7 + 6.7.8 + 7.8.9
Tính tổng E=1.2.3+3.4.5+5.6.7+...+99.100.101
1.2.3+2.3.4+3.4.5+4.5.6+5.6.7+6.7.8+7.8.9+8.9.10