Question

[vũ linh trang]

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