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

Toán Lớp 6: so sánh a=2/3+14/15+34/35+62/63+98/99+142/143+194/195 với b=5+1/2^2+1/3^3+1/4^4+1/5^5+1/6^6+1/7^7

Home/ Toán Lớp 6: so sánh a=2/3+14/15+34/35+62/63+98/99+142/143+194/195 với b=5+1/2^2+1/3^3+1/4^4+1/5^5+1/6^6+1/7^7

Toán Lớp 6: so sánh a=2/3+14/15+34/35+62/63+98/99+142/143+194/195 với b=5+1/2^2+1/3^3+1/4^4+1/5^5+1/6^6+1/7^7

Tháng Hai 14, 2023 Toán học 1 Comment 0 views

Toán Lớp 6: so sánh a=2/3+14/15+34/35+62/63+98/99+142/143+194/195 với b=5+1/2^2+1/3^3+1/4^4+1/5^5+1/6^6+1/7^7

Comments ( 1 )

  1. huenthanh97
    huenthanh97
    14 Tháng Hai, 2023 at 1:25 chiều
    Reply
    A=2/3+14/15+34/35+62/63+98/99+142/143+194/195
    =>A=(1-1/3)+(1-1/15)+(1-1/35)+(1-1/63)+(1-1/99)+(1-1/143)+(1/195)
    =>A=7-(1/3+1/15+1/35+1/63+1/99+1/143+1/195)
    =>A=7-(1/1.3+1/3.5+1/5.7+1/7.9+1/9.11+1/11.13+1/13.15)
    =>A=7-1/2(2/1.3+2/3.5+2/5.7+2/7.9+2/9.11+2/11.13+2/13.15)
    =>A=7-1/2(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13+1/13-1/15)
    =>A=7-1/2(1-1/15)
    =>A=7-1/2. 14/15
    =>A=7-7/15>6 (Vì 7/15∉N text(*))
    B=5-1/2^2+1/3^3+1/4^4+1/5^5+1/6^6+1/7^7
    =>B=5-(1/2^2+1/3^3+1/4^4+1/5^5+1/6^6+1/7^7)
    =>B<5
    =>A>6>5>B
    Vậy A>B

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

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