Tính tổng B = 2/3.5 + 2/5.7 + + 2/97.99
Tính tổng \(B = \frac{2}{{3.5}} + \frac{2}{{5.7}} + ... + \frac{2}{{97.99}}\).
\(B = \frac{2}{{3.5}} + \frac{2}{{5.7}} + ... + \frac{2}{{97.99}}\)
\(B = \frac{1}{3} - \frac{1}{5} + \frac{1}{5} - \frac{1}{7} + ... + \frac{1}{{97}} - \frac{1}{{99}}\)
\(B = \frac{1}{3} - \frac{1}{{99}}\)
\(B = \frac{{32}}{{99}}\).