Question

tinh nhanh:s=2/5.7+2/7.9+2/9.11+...+2/93.95+3/95.98+4/98.102+5/102.107+2012/107.2119

Answer 1

S=\(\frac{2}{5.7}\)+\(\frac{2}{7.9}\)+....+\(\frac{2}{93.95}\)+\(\frac{3}{95.98}\)+\(\frac{4}{98.102}\)+\(\frac{5}{102.107}\)+\(\frac{2012}{107.2119}\)

S=\(\frac{1}{5}\)-\(\frac{1}{7}\)+\(\frac{1}{7}\)-\(\frac{1}{9}\)+....+\(\frac{1}{93}\)-\(\frac{1}{95}\)+\(\frac{1}{95}\)-\(\frac{1}{98}\)+\(\frac{1}{98}\)-\(\frac{1}{102}\)+\(\frac{1}{102}\)-\(\frac{1}{107}\)+\(\frac{1}{107}\)-\(\frac{1}{2119}\)

S=\(\frac{1}{5}\)-\(\frac{1}{2119}\)

S=\(\frac{2114}{10595}\)