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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: a. 1/2 – 1. 3.7 – 1/ 7.11 – 1/11.5 – 1/15.19-1/19.23-1/23.27 b, 1-1/5.10-1/10.15-…- 1/95.100

Tháng Mười Một 13, 2022 Toán học 1 Comment 0 views

Toán Lớp 7: a. 1/2 – 1. 3.7 – 1/ 7.11 – 1/11.5 – 1/15.19-1/19.23-1/23.27
b, 1-1/5.10-1/10.15-…- 1/95.100

Comments ( 1 )

  1. baoquyen
    baoquyen
    13 Tháng Mười Một, 2022 at 9:58 chiều
    Reply
    a, 1/2 – 1/( 3 . 7 ) – 1/( 7 . 11 ) – 1/( 11 . 15 ) – 1/( 15 . 19 ) – 1/( 19 . 23 ) – 1/( 23 . 27 )
    = 1/2 – ( 1/( 3 . 7 ) + 1/( 7 . 11 ) + ….. + 1/( 23 . 27 ) )
    = 1/2 – ( 4/( 3 . 7 ) + 4/( 7 . 11 ) + …. + 4/( 23 . 27 ) ) . 1/4
    = 1/2 – ( 1/3 – 1/7 + 1/7 – 1/11 + …. + 1/23 – 1/27 ) . 1/4
    = 1/2 – ( 1/3 – 1/27 ) . 1/4
    = 1/2 – 8/27 . 1/4
    = 1/2 – 2/27
    = 23/54
    b, 1 – 1/( 5 . 10 ) – 1/( 10 . 15 ) – …. – 1/( 95 . 100 )
    = 1 – ( 1/( 5 . 10 ) + 1/( 10 . 15 ) + …. + 1/( 95 . 100 ) )
    = 1 – ( 5/( 5 . 10 ) + 5/( 10 . 15 ) + …. + 5/( 95 . 100 ) ) . 1/5
    = 1 – ( 1/5 – 1/10 + 1/10 – 1/15 + …. + 1/95 – 1/100 ) . 1/5
    = 1 – ( 1/5 – 1/100 ) . 1/5
    = 1 – 19/100 . 1/5
    = 1 – 19/500
    = 481/500

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222-9+11+12:2*14+14 = ? ( )

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