tính giá trị biểu thức: 1 1 1 ... 2 4 2 s n
Giải thích
A=1−12−122−123−124−...−1210=1−12+122+123+124+...+1210
Đặt:
H=12+122+123+124+...+1210⇔2H=1+12+122+123+124+...+129
⇔H=2H−H=1−1210⇔A=1−1−1210=1210
A=1−12−122−123−124−...−1210=1−12+122+123+124+...+1210
Đặt:
H=12+122+123+124+...+1210⇔2H=1+12+122+123+124+...+129
⇔H=2H−H=1−1210⇔A=1−1−1210=1210