Question

[Mai Thi Cam Nhung]

Chuứng minh rằng:

A=\(\frac{1}{2}-\frac{2}{2^2}+\frac{3}{2^3}-\frac{4}{2^4}+.....+\frac{99}{2^{99}}-\frac{100}{^{ }2^{100}}< \frac{2}{9}\)