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

Toán Lớp 6: so sánh biểu thức với 1 A= 2/1.3 – 2/2.4 + 2/3.5 – 2/4.6 + 2/5.7 – 2/6.8 + 2/7.9 – 2/8.10 + 2/9.11 – 2/10.12

Toán Lớp 6: so sánh biểu thức với 1
A= 2/1.3 – 2/2.4 + 2/3.5 – 2/4.6 + 2/5.7 – 2/6.8 + 2/7.9 – 2/8.10 + 2/9.11 – 2/10.12

Comments ( 2 )

  1. text{Giải đáp:}
    A < 1 
    text{Lời giải và giải thích chi tiết:}
    A = 2/1.3 – 2/2.4 + 2/3.5 – 2/4.6 + 2/5.7 – 2/6.8 + 2/7.9 – 2/8.10 + 2/9.11 – 2/10.12
    A = 2/3 – 2/8 + 2/15 – 2/24 + 2/35 – 2/48 + 2/63 – 2/80 + 2/99 – 2/120
    A = 2/3 – 1/4 + 2/15 – 1/12 + 2/35 – 1/24 + 2/63 – 1/40 + 2/99 – 1/60
    A = (2/3 – 1/4) + (2/15 – 1/12) + (2/35 – 1/24) + (2/63 – 1/40) + (2/99 – 1/60)
    A = 5/12 + 1/20 + 13/840 + 17/2520 + 7/1980
    A = (5/12 + 1/20) + (13/840 + 17/2520 + 7/1980)
    A = 7/15 + 17/660
    A = 65/132
    → 65/132 < 1
    ⇒ A < 1  

  2. Giải đáp:
    A<1
    Lời giải và giải thích chi tiết:
     

    toan-lop-6-so-sanh-bieu-thuc-voi-1-a-2-1-3-2-2-4-2-3-5-2-4-6-2-5-7-2-6-8-2-7-9-2-8-10-2-9-11-2-1

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

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