Question

Tính nhanh

A=1/2+1/4+1/8+1/16+1/32+1/64+1/128

B=1/1x2+1/2x3+1/3x4+............1/99x100

Answer 1

A=1-1/2+1/2-1/3+1/3-1/4+...+1/64-1/128

A=1-1/128

A=127/128

Vậy A=\(\frac{127}{128}\)

Answer 2

B=1-1/2+1/2-1/3+1/3-1/4+...+1/99-1/100

B=1-1/100

B=99/100

Vậy B=\(\frac{99}{100}\)