Bạn tham khảo :
$2G= \dfrac{2}{99} - \dfrac{2}{99.97} - \dfrac{2}{97.95}- ... - \dfrac{2}{5.3} - \dfrac{2}{3.1}$
$2G = \dfrac{1}{99} - ( \dfrac{2}{1.3} + \dfrac{2}{3.5} + ... +\dfrac{2}{97.99})$
$2G = \dfrac{1}{99} - ( 1 - \dfrac{1}{3} + \dfrac{1}{3} - \dfrac{1}{5} + ... +\dfrac{1}{97} - \dfrac{1}{99}$
$2G = \dfrac{1}{99} - (1 - \dfrac{1}{99})$
$2G = \dfrac{1}{99} - \dfrac{98}{99}$
$2G = \dfrac{-97}{99}$
$G = \dfrac{-97}{198}$