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20 tháng 5 2016

A = 1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90 =

 

1-1/2+1-1/6+1-1/12+1-1/20+1-1/30+1-1/42+1-1/56+1-1/72+1-1/90 =

 

9 – (1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90) =

 

9 – [1/(1x2)+1/(2x3)+1/(3x4)+1/(4x5)+1/(5x6)+1/(6x7)+1/(7x8)+1/(8x9)+1/(9x10)] =

 

9 – ( 1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10) =

 

9 – (1 – 1/10) = 9 – 9/10 = 81/10

20 tháng 6 2018

Đặt:

Nhận xét

Vậy

12 tháng 1 2017

a: n(omega)=100

n(A)=12

=>P=12/100=3/25

b: n(B)=25+17+13+7=62

=>P(B)=62/100=31/50

c: n(C)=12+6+20+25=63

=>P(C)=63/100

24 tháng 12 2018

a ) 17 6 b ) − 43 30 c ) − 5 36

d ) 9 20 . e ) 11 3 . f ) 1 12

8 tháng 1 2018

a)  1 2 + − 2 3 + 1 6 + 3 7 = 3 6 + − 4 6 + 1 6 + 3 7 = 3 7

b)  1 2 + 2 8 + 3 4 + 4 5 + 5 6 = 30 60 + 40 60 + 45 60 + 48 60 + 50 60 = 71 5

9 tháng 12 2018

a)  1 2 + 2 3 + 3 4 + 4 5 + 5 6 = 30 60 + 40 60 + 45 60 + 48 60 + 50 60 = 71 20

b)  4 6 + 27 81 = 4 6 + 2 6 = 1

10 tháng 9 2018

a) 3.              

b) 1.

c ) 1 2 + − 2 3 + 1 6 + 3 7 = 3 6 + − 4 6 + 1 6 + 3 7 = 3 7 ; d ) 1 2 + 2 8 + 3 4 + 4 5 + 5 6 = 30 60 + 40 60 + 45 60 + 48 60 + 50 60 = 71 5

 

`= 1 - 1/2 + 1 - 1/6 + ... + 1 - 1/56`

`= 1 - 1/(1.2) + 1 - 1/(2.3) + ... + 1 - 1/(7.8)`

`= 7 - (1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4+ 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8`.

`= 8 - 1/8`

`= 63/64`.

16 tháng 5 2022

`A=1/2+5/6+11/12+19/20+29/30+41/42+55/56`

`A=1-1/2+1-1/6+1-1/12+1-1/20+1-1/30+1-1/42+1-1/56`

`A=(1+1+1+1+1+1+1)-(1/2+1/6+1/12+....+1/56)`

`A=7-(1/[1xx2]+1/[2xx3]+1/[3xx4]+....+1/[7xx8])`

`A=7-(1-1/2+1/2-1/3+1/3-1/4+....+1/7-1/8)`

`A=7-(1-1/8)`

`A=7-(8/8-1/8)`

`A=7-7/8`

`A=56/8-7/8=49/8`

16 tháng 11 2023

gom vô

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16 tháng 11 2023

(1111+8889)+(2222+7778)+(4444+5556)

=10000+10000+10000
Đây nha