Question

Tính nhanh :1/2+1/6+1/12+1/20+...+1/100

Answer 1

phải thay 1/100 thành 1/110

1/2+1/6+1/12+1/20+...+1/100

=1/1x2+1/2x3+1/3x4+1/4x5+...+1/10x11

=1-1/11

=10/11
 

Answer 2

Đặt A = 1/2 + 1/6 + 1/12 + ... + 1/110

=> A = 1/1.2 + 1/2.3 + 1/3.4 + ... + 1/10.11

=> A = 1/1 - 1/2 + 1/2 - 1/3 + .... + 1/10 - 1/11

=> A = 1 - 1/11

=> A = 10/11

Answer 3

10/11 mà !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Answer 4

sorry, 1/110 nha

Answer 5

nam lầy