Tính nhanh 4/1.3 + 4/3.5 + 4/5.7 +…+ 4/99.101

----- Nội dung ảnh -----
2) A =
\[
\frac{4}{1.3} + \frac{4}{3.5} + \frac{4}{5.7} + \ldots + \frac{4}{99.101}
\]
\[
\frac{2}{2} \frac{2}{2} \frac{2}{2}
\]