cm 1/1.2+1/3.4+1/5.6+…..+1/99.100=1/51+1/52+…..+1/100 17/08/2021 Bởi aihong cm 1/1.2+1/3.4+1/5.6+…..+1/99.100=1/51+1/52+…..+1/100
$\frac{1}{1.2}$ + $\frac{1}{3.4}$ + $\frac{1}{5.6}$ + … +$\frac{1}{99.100}$ = = 1 – $\frac{1}{2}$ + $\frac{1}{3}$ – $\frac{1}{4}$ + $\frac{1}{5}$ – $\frac{1}{6}$ + … + $\frac{1}{99}$ – $\frac{1}{100}$ = 1 + $\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{4}$ + $\frac{1}{5}$ + $\frac{1}{6}$ + … + $\frac{1}{99}$ + $\frac{1}{100}$ – 2( $\frac{1}{2}$ + $\frac{1}{4}$ + $\frac{1}{6}$ + … + $\frac{1}{100}$) = 1 + $\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{4}$ + $\frac{1}{5}$ + $\frac{1}{6}$ + … + $\frac{1}{99}$ + $\frac{1}{100}$ – ( 1 + $\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{4}$ + $\frac{1}{5}$ + $\frac{1}{6}$ + … + $\frac{1}{50}$) =( $\frac{1}{51}$ + $\frac{1}{52}$ + $\frac{1}{53}$ + $\frac{1}{54}$ + $\frac{1}{55}$ + … + $\frac{1}{100}$) Bình luận
$\frac{1}{1.2}$ + $\frac{1}{3.4}$ + $\frac{1}{5.6}$ + … +$\frac{1}{99.100}$
= = 1 – $\frac{1}{2}$ + $\frac{1}{3}$ – $\frac{1}{4}$ + $\frac{1}{5}$ – $\frac{1}{6}$ + … + $\frac{1}{99}$ – $\frac{1}{100}$
= 1 + $\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{4}$ + $\frac{1}{5}$ + $\frac{1}{6}$ + … + $\frac{1}{99}$ + $\frac{1}{100}$ – 2( $\frac{1}{2}$ + $\frac{1}{4}$ + $\frac{1}{6}$ + … + $\frac{1}{100}$)
= 1 + $\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{4}$ + $\frac{1}{5}$ + $\frac{1}{6}$ + … + $\frac{1}{99}$ + $\frac{1}{100}$ – ( 1 + $\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{4}$ + $\frac{1}{5}$ + $\frac{1}{6}$ + … + $\frac{1}{50}$)
=( $\frac{1}{51}$ + $\frac{1}{52}$ + $\frac{1}{53}$ + $\frac{1}{54}$ + $\frac{1}{55}$ + … + $\frac{1}{100}$)