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

0 bình luận về “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”

1. `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`

    

   Trả lời

2. $a,\dfrac{6}{1.2}$ $+\dfrac{6}{2.3}+$ $\dfrac{6}{3.4}$ $+\dfrac{6}{4.5}+$ $…+\dfrac{6}{98.99}$ $+\dfrac{6}{99.100}$

   $=6(\dfrac{1}{1.2}$ $+\dfrac{1}{2.3}+$ $\dfrac{1}{3.4}$ $+\dfrac{1}{4.5}+$ $…+\dfrac{1}{98.99}$ $+\dfrac{1}{99.100})$

   $=6(1-\dfrac{1}{2}$ $+\dfrac{1}{2}-$ $\dfrac{1}{3}$ $+\dfrac{1}{3}+$ $…-\dfrac{1}{99}$ $+\dfrac{1}{99}-\dfrac{1}{100})$

   $=6(1-\dfrac{1}{100})$

   $=6.\dfrac{99}{100}$

   $=\dfrac{297}{50}$

   $b,\dfrac{5}{1.4}$ $+\dfrac{5}{4.7}+$ $\dfrac{5}{7.10}$ $+\dfrac{5}{10.14}+$ $…+\dfrac{5}{94.97}$ $+\dfrac{5}{97.100}$

   $=\dfrac35(\dfrac{3}{1.4}$ $+\dfrac{3}{4.7}+$ $\dfrac{3}{7.10}$ $+\dfrac{3}{10.14}+$ $…+\dfrac{3}{94.97}$ $+\dfrac{3}{97.100})$

   $=\dfrac35(1-\dfrac{1}{4}$ $+\dfrac{1}{4}-$ $\dfrac{1}{7}$ $+\dfrac{1}{7}+$ $…-\dfrac{1}{97}$ $+\dfrac{1}{97}-\dfrac{1}{100})$

   $=\dfrac35(1-\dfrac{1}{100})$

   $=\dfrac35.\dfrac{99}{100}$

   $=\dfrac{297}{500}$

   Trả lời