1.
a) A= \(\frac{3}{1.4}\)+\(\frac{3}{4.7}\)+\(\frac{3}{7.10}\)+...+\(\frac{3}{97.100}\)
b) B= \(\frac{1}{2.5}\)+\(\frac{1}{8.11}\)+...+\(\frac{1}{92.95}\)+\(\frac{1}{95.98}\)
2. Tìm STN n
\(\frac{1}{3}\)+\(\frac{1}{6}\)+\(\frac{1}{10}\)+...+\(\frac{2}{n.\left(n+1\right)}\)=\(\frac{1999}{2000}\)