Bài 25: Tính A= 2^100 – 2^99 – 2^98 -…- 2^2 – 2 – 1 B= 1/1.2.3 + 1/2.3.4 + 1/3.4.5 +…+1/37.38.39 C= 1.2 + 2.3 + 3.4 +…+ 99.100 D= (1-1/3).(1-1/6

Bởi

Bài 25: Tính
A= 2^100 – 2^99 – 2^98 -…- 2^2 – 2 – 1
B= 1/1.2.3 + 1/2.3.4 + 1/3.4.5 +…+1/37.38.39
C= 1.2 + 2.3 + 3.4 +…+ 99.100
D= (1-1/3).(1-1/6).(1-1/10).(1-1/15)…(1-1/780)
E=5/2.1 + 4/1.11 + 3/11.2 + 1/2.15 + 13/15.4
Bài 26: Chứng minh:
a) 1/1.2 + 1/3.4 +1/5.6 +…+ 1/99.100 = 1/51 + 1/52 + 1/53 + …+ 1/100
b) 7/12 < 1/1.2 +1/3.4 + 1/5.6+...+1/99.100 < 5/6 Giúp mk zới nhaaa, chiều nay mk thi r

0 bình luận về “Bài 25: Tính A= 2^100 – 2^99 – 2^98 -…- 2^2 – 2 – 1 B= 1/1.2.3 + 1/2.3.4 + 1/3.4.5 +…+1/37.38.39 C= 1.2 + 2.3 + 3.4 +…+ 99.100 D= (1-1/3).(1-1/6”

  1. Bài 25:

    A         =  2^100 – 2^99 – 2^98 -…- 2^2 – 2 – 1

    2A       =  2 . ( 2^100 – 2^99 – 2^98 – … – 2^2 -2-1)

    2A       =  2^101 – 2^100 – 2^99 – … – 2^2 – 2

    2A – A =  2^101 –  2^100 – 2^100 +1

    A         =  2^101 -2 . 2^100 + 1

    A         =  2^101 – 2^101 + 1

    A         =  1

    B = 1/1.2.3 + 1/2.3.4 + 1/3.4.5 +…+1/37.38.39

    B = 1/1.2 – 1/2.3 + 1/2.3 – 1/3.4 +….+ 1/37.38 – 1/38.39

    B = 1/1.2 – 1/38/39 

    B = 370/714

    C   = 1.2 + 2.3 +…+ 99.100

    3C = 1.2.3 + 2.3.3 + … + 99.100.3

    3C = 1.2 . (3-0) + 2.3 . (4-1) +…+ 99.100 . (101-98)

    C   = 99 . 100 . 101/3

    C   = 333300

    D = (1-1/3) . (1-1/6) . (1-1/10) . (1-1/15) … (1-1/780)

    D = 2/3 . 5/6 . 9/10 …… . 779/780

    D = 4/6 . 10/12 . 18/20 ……1558/1560

    D = 1.4/2.3 . 2.5/3.4 . 3.6/4.5 …… 38.4/39.40

    D = 1.2.3….38 / 2.3.4….39 . 4.5….41/ 3.4…..40

    D = 1/39 . 41/3

    D = 41/117

    E    =5/2.1 + 4/1.11 + 3/11.2 + 1/2.15 + 13/15.4

    E/7 = 5/2.7 + 4/11.7 + 3/11.14 + 1/14.15 + 13/15.4

    E/7 =1/2 – 1/7 + 1/7 – …  + 1/15  1/28

    E/7 = 1/2 – 1/28

    E/7 = 13/28

    E     = 13/28 . 7 

    E     = 13/4

    Bạn ơi, xl nha, mik ko bt làm bài chứng minh!

     

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  2.    A= 2^100 – 2^99 – 2^98 -…- 2^2 – 2 – 1

    2A = 2 . [ 2^100 – 2^99 – 2^98 – … – 2^2 -2-1

    2A = 2^101 – 2^100 – 2^99 – … – 2^2 – 2

    2A – A = 2^101 –  2^100 – 2^100 +1

    A   = 2^101 -2 . 2^100 + 1

    A   = 2^101 – 2^101 + 1

    A   =       1

    B= 1/1.2.3 + 1/2.3.4 + 1/3.4.5 +…+1/37.38.39

    B = 1/1.2 – 1/2.3 + 1/2.3 – 1/3.4 +….+ 1/37.38 – 1/38.39

    B = 1/1.2 – 1/38/39 

    B = 370/714

    D= (1-1/3).(1-1/6).(1-1/10).(1-1/15)…(1-1/780)

    D = 2/3 . 5/6 . 9/10 …… . 779/780

    D = 4/6 . 10/12 . 18/20 ……1558/1560

    D = 1.4/2.3 . 2.5/3.4 . 3.6/4.5 …… 38.4/39.40

    D = 1.2.3….38 / 2.3.4….39 . 4.5….41/ 3.4…..40

    D = 1/39 . 41/3

    D = 41/117

        E=5/2.1 + 4/1.11 + 3/11.2 + 1/2.15 + 13/15.4

    E/7 = 5/2.7 + 4/11.7 + 3/11.14 + 1/14.15 + 13/15.4

    E/7 =1/2 – 1/7 + 1/7 – …  + 1/15  1/28

    E/7 = 1/2 – 1/28

    E/7 = 13/28

    E     = 13/28 . 7 

    E     = 13/4

       Chúc chiều thi tốt!!

     

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