A=1/6+1/12+1/20+…+1/90+1/100 Tính tổng?

2 bình luận về “A=1/6+1/12+1/20+…+1/90+1/100 Tính tổng?”

1. Ta có: A = 1/6 + 1/(12) + 1/(20) + … + 1/(90) + 1/(100)

   => A = 1/(2.3) + 1/(3.4) + 1/(4.5) + … + 1/(9.10) + 1/(100)

   => A = 1/2 – 1/3 +1/3 -1/4 + 1/4 -1/5 + … + 1/9 – 1/(10) + 1/(100)

   => A = 1/2 – 1/(10) + 1/(100)

   => A = 2/5 + 1/(100)

   => A = (41)/(100)

   Vậy A = (41)/(100)

   $#duong612009$

   Trả lời
2. A=1/6+1/12+1/20+…+1/90+1/100

   A=1/(2xx3)+1/(3xx4)+1/(4xx5)+…+1/(9xx10)+1/(10xx10)

   A=1/2-1/3+1/3-1/4+1/4-1/5+….+1/9-1/10+1/10-1/10

   A=1/2-\cancel(1/3)+cancel(1/3)-cancel(1/4)+cancel(1/4)-cancel(1/5)+….+cancel(1/9)-cancel(1/10)+cancel(1/10)-1/10

   A=1/2-1/10

   A=2/5

   Trả lời