2^2/3*5 + 2^2/5*7 + 2^2/7*9 +….+2^2/97*99 06/08/2021 Bởi Allison 2^2/3*5 + 2^2/5*7 + 2^2/7*9 +….+2^2/97*99
`2^2/{3.5}+2^2/{5.7}+2^2/[7.9]+….+2^2/[97.99]` `=2.(2/3.5+2/5.7+2/7.9+….+2/97.99)` `=2.(1/3-1/5+1/5-1/7+…+1/97-1/99)` `=2.(1/3-1/99)` `=2.32/99` `=64/99` $@Race2k53$ Xin hay nhất ! Bình luận
$\frac{2^{2} }{3.5}$ +$\frac{2^{2} }{5.7}$ +$\frac{2^{2} }{7.9}$ +…+$\frac{2^{2} }{97.99}$ =2.($\frac{2}{3.5}$ +$\frac{2}{5.7}$ +$\frac{2}{7.9}$ +…+$\frac{2}{97.99}$ ) =2.($\frac{1}{3}$ -$\frac{1}{5}$ +$\frac{1}{5}$ -$\frac{1}{7}$ +$\frac{1}{7}$ -$\frac{1}{9}$ +…+$\frac{1}{97}$ -$\frac{1}{99}$ ) =2.($\frac{1}{3}$ -$\frac{1}{99}$ ) =2.$\frac{33}{99}$ -$\frac{1}{99}$ ) =2.$\frac{32}{99}$ =$\frac{64}{99}$ . Bình luận
`2^2/{3.5}+2^2/{5.7}+2^2/[7.9]+….+2^2/[97.99]`
`=2.(2/3.5+2/5.7+2/7.9+….+2/97.99)`
`=2.(1/3-1/5+1/5-1/7+…+1/97-1/99)`
`=2.(1/3-1/99)`
`=2.32/99`
`=64/99`
$@Race2k53$
Xin hay nhất !
$\frac{2^{2} }{3.5}$ +$\frac{2^{2} }{5.7}$ +$\frac{2^{2} }{7.9}$ +…+$\frac{2^{2} }{97.99}$
=2.($\frac{2}{3.5}$ +$\frac{2}{5.7}$ +$\frac{2}{7.9}$ +…+$\frac{2}{97.99}$ )
=2.($\frac{1}{3}$ -$\frac{1}{5}$ +$\frac{1}{5}$ -$\frac{1}{7}$ +$\frac{1}{7}$ -$\frac{1}{9}$ +…+$\frac{1}{97}$ -$\frac{1}{99}$ )
=2.($\frac{1}{3}$ -$\frac{1}{99}$ )
=2.$\frac{33}{99}$ -$\frac{1}{99}$ )
=2.$\frac{32}{99}$
=$\frac{64}{99}$ .