Tính A, ta có

giúp
----- Nội dung ảnh -----
A = \(\frac{1}{3.8} + \frac{1}{8.13} + \frac{1}{13.18} + \ldots + \frac{1}{33.38}\)
\(\frac{1}{21} + \frac{1}{15} + \frac{1}{27} + \frac{1}{9} + \frac{1}{33}\)
\(\frac{1}{3.10} + \frac{1}{10.15} + \frac{1}{15.24} + \frac{1}{24.27} + \frac{1}{27.38}\)