a,6/1.2+6/2.3+6/3.4+6/4.5+…+6/99 100 b,5/1.4+5/4.7+5/7.10+…+5/97.100 NhAnh nha 07/12/2021 Bởi Eloise a,6/1.2+6/2.3+6/3.4+6/4.5+…+6/99 100 b,5/1.4+5/4.7+5/7.10+…+5/97.100 NhAnh nha
`a,` `6/1.2+6/2.3+6/3.4+6/4.5+…+6/99.100` `= 6.(1 – 1/2 + 1/2 – 1/3 + 1/3 + 1/4 + … + 1/99 – 1/100 )` ` =6.(1 – 1/100 )` ` = 6. 99/100` ` = 594/100 = 297/50` `b,` `5/1.4+5/4.7+5/7.10+…+5/97.100` `=5.(3/1.4 + 3/4.7 + … + 3/97.100 )` `=5/3.(1/1.4+1/4.7+1/7.10+…+1/97.100)` ` = 5/3.(1 – 1/4 + 1/4 – 1/7 + … + 1/97 – 1/100 )` ` =5/3 .(1 – 1/100 )` ` =5/3 . 99/100 =495/300` Bình luận
$a,\dfrac{6}{1.2}$ $+\dfrac{6}{2.3}+$ $\dfrac{6}{3.4}$ $+\dfrac{6}{4.5}+$ $…+\dfrac{6}{98.99}$ $+\dfrac{6}{99.100}$ $=6(\dfrac{1}{1.2}$ $+\dfrac{1}{2.3}+$ $\dfrac{1}{3.4}$ $+\dfrac{1}{4.5}+$ $…+\dfrac{1}{98.99}$ $+\dfrac{1}{99.100})$ $=6(1-\dfrac{1}{2}$ $+\dfrac{1}{2}-$ $\dfrac{1}{3}$ $+\dfrac{1}{3}+$ $…-\dfrac{1}{99}$ $+\dfrac{1}{99}-\dfrac{1}{100})$ $=6(1-\dfrac{1}{100})$ $=6.\dfrac{99}{100}$ $=\dfrac{297}{50}$ $b,\dfrac{5}{1.4}$ $+\dfrac{5}{4.7}+$ $\dfrac{5}{7.10}$ $+\dfrac{5}{10.14}+$ $…+\dfrac{5}{94.97}$ $+\dfrac{5}{97.100}$ $=\dfrac35(\dfrac{3}{1.4}$ $+\dfrac{3}{4.7}+$ $\dfrac{3}{7.10}$ $+\dfrac{3}{10.14}+$ $…+\dfrac{3}{94.97}$ $+\dfrac{3}{97.100})$ $=\dfrac35(1-\dfrac{1}{4}$ $+\dfrac{1}{4}-$ $\dfrac{1}{7}$ $+\dfrac{1}{7}+$ $…-\dfrac{1}{97}$ $+\dfrac{1}{97}-\dfrac{1}{100})$ $=\dfrac35(1-\dfrac{1}{100})$ $=\dfrac35.\dfrac{99}{100}$ $=\dfrac{297}{500}$ Bình luận
`a,`
`6/1.2+6/2.3+6/3.4+6/4.5+…+6/99.100`
`= 6.(1 – 1/2 + 1/2 – 1/3 + 1/3 + 1/4 + … + 1/99 – 1/100 )`
` =6.(1 – 1/100 )`
` = 6. 99/100`
` = 594/100 = 297/50`
`b,`
`5/1.4+5/4.7+5/7.10+…+5/97.100`
`=5.(3/1.4 + 3/4.7 + … + 3/97.100 )`
`=5/3.(1/1.4+1/4.7+1/7.10+…+1/97.100)`
` = 5/3.(1 – 1/4 + 1/4 – 1/7 + … + 1/97 – 1/100 )`
` =5/3 .(1 – 1/100 )`
` =5/3 . 99/100 =495/300`
$a,\dfrac{6}{1.2}$ $+\dfrac{6}{2.3}+$ $\dfrac{6}{3.4}$ $+\dfrac{6}{4.5}+$ $…+\dfrac{6}{98.99}$ $+\dfrac{6}{99.100}$
$=6(\dfrac{1}{1.2}$ $+\dfrac{1}{2.3}+$ $\dfrac{1}{3.4}$ $+\dfrac{1}{4.5}+$ $…+\dfrac{1}{98.99}$ $+\dfrac{1}{99.100})$
$=6(1-\dfrac{1}{2}$ $+\dfrac{1}{2}-$ $\dfrac{1}{3}$ $+\dfrac{1}{3}+$ $…-\dfrac{1}{99}$ $+\dfrac{1}{99}-\dfrac{1}{100})$
$=6(1-\dfrac{1}{100})$
$=6.\dfrac{99}{100}$
$=\dfrac{297}{50}$
$b,\dfrac{5}{1.4}$ $+\dfrac{5}{4.7}+$ $\dfrac{5}{7.10}$ $+\dfrac{5}{10.14}+$ $…+\dfrac{5}{94.97}$ $+\dfrac{5}{97.100}$
$=\dfrac35(\dfrac{3}{1.4}$ $+\dfrac{3}{4.7}+$ $\dfrac{3}{7.10}$ $+\dfrac{3}{10.14}+$ $…+\dfrac{3}{94.97}$ $+\dfrac{3}{97.100})$
$=\dfrac35(1-\dfrac{1}{4}$ $+\dfrac{1}{4}-$ $\dfrac{1}{7}$ $+\dfrac{1}{7}+$ $…-\dfrac{1}{97}$ $+\dfrac{1}{97}-\dfrac{1}{100})$
$=\dfrac35(1-\dfrac{1}{100})$
$=\dfrac35.\dfrac{99}{100}$
$=\dfrac{297}{500}$