2 / 1 x 3 + 2 / 3 x 5 + 2 / 5 x 7 + ….. + 2 / 2017 x 2019 08/09/2021 Bởi Arianna 2 / 1 x 3 + 2 / 3 x 5 + 2 / 5 x 7 + ….. + 2 / 2017 x 2019
$\frac{2}{1×3}$+$\frac{2}{3×5}$+$\frac{2}{5×7}$+……+$\frac{2}{2017×2019}$ =1-$\frac{1}{3}$ +$\frac{1}{3}$-$\frac{1}{5}$ +$\frac{1}{5}$ -$\frac{1}{7}$+……+$\frac{1}{2017}$-$\frac{1}{2019}$ =1-$\frac{1}{2019}$ =$\frac{2018}{2019}$ Bình luận
Giải thích các bước giải: $\dfrac{2}{1 \times 3} + \dfrac{2}{3 \times 5} + \dfrac{2}{5 \times 7} + … + \dfrac{2}{2017 \times 2019}$ $= 1 – \dfrac{1}{3} + \dfrac{1}{3} – \dfrac{1}{5} + \dfrac{1}{5} – \dfrac{1}{7} + … + \dfrac{1}{2017} – \dfrac{1}{2019}$ $= 1 – \dfrac{1}{2019}$ $= \dfrac{2018}{2019}$ Bình luận
$\frac{2}{1×3}$+$\frac{2}{3×5}$+$\frac{2}{5×7}$+……+$\frac{2}{2017×2019}$
=1-$\frac{1}{3}$ +$\frac{1}{3}$-$\frac{1}{5}$ +$\frac{1}{5}$ -$\frac{1}{7}$+……+$\frac{1}{2017}$-$\frac{1}{2019}$
=1-$\frac{1}{2019}$
=$\frac{2018}{2019}$
Giải thích các bước giải:
$\dfrac{2}{1 \times 3} + \dfrac{2}{3 \times 5} + \dfrac{2}{5 \times 7} + … + \dfrac{2}{2017 \times 2019}$
$= 1 – \dfrac{1}{3} + \dfrac{1}{3} – \dfrac{1}{5} + \dfrac{1}{5} – \dfrac{1}{7} + … + \dfrac{1}{2017} – \dfrac{1}{2019}$
$= 1 – \dfrac{1}{2019}$
$= \dfrac{2018}{2019}$