Question

HELP ME

Answer 1

-1

Answer 2

-1

Answer 3

A = -2/1.3 - 2/5.7 - ... - 2/19.21 - 2/25.27 - 1/27

A = -(1 - 1/3 + 1/3 - 1/5 + 1/5 -1/7 + ... + 1/25 - 1/27) - 1/27

A = -(1 - 1/27 ) -1/27

A = -1

Answer 4

vòng nào đấy

Answer 5

vừa thi vừa tra mạng à