S=\(\frac{5}{2\cdot3\cdot4}\)+\(\frac{5}{3\cdot4\cdot5}\)+...+\(\frac{5}{99\cdot100\cdot101}\)
S=\(\frac{5}{2}\)*(\(\frac{2}{2\cdot3\cdot4}\)+\(\frac{2}{3\cdot4\cdot5}\)+...+\(\frac{2}{99\cdot100\cdot101}\))
S=\(\frac{5}{2}\)*(\(\frac{1}{2\cdot3}\)-\(\frac{1}{3\cdot4}\)+\(\frac{1}{3\cdot4}\)-\(\frac{1}{4\cdot5}\)+...+\(\frac{1}{99\cdot100}\)-\(\frac{1}{100\cdot101}\))
S=\(\frac{5}{2}\)*(\(\frac{1}{6}\)-\(\frac{1}{10100}\))
S=\(\frac{5}{2}\)*\(\frac{5047}{30300}\)
S=\(\frac{25235}{60600}\)(bạn tự rút gọn)
uwk....chiều tớ học về tớ làm cho!giờ tớ đang vội đi học
