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

Toán Lớp 4: 2/3 + 2/15 + 2/35 + 2/63 + 2/99 =?

Toán Lớp 4: 2/3 + 2/15 + 2/35 + 2/63 + 2/99 =?

Comments ( 2 )

  1. 2/3 + 2/15 + 2/35 + 2/63 + 2/99
    = 2/{1 × 3} + 2/{3 × 5} + 2/{5 × 7} + 2/{7 × 9} + 2/{9 × 11}
    = 1/1 – 1/3 + 1/3 – 1/5 + 1/5 – 1/7 + 1/7 – 1/9 + 1/9 – 1/11
    = 1/1 – 1/11
    = 10/11
    #dtkc

  2. Giải đáp + Lời giải và giải thích chi tiết:
    2/3+2/15+2/35+2/63+2/99
    =2xx(1/3+1/15+1/35+1/63+1/99)
    =2xx(1/(1xx3)+1/(3xx5)+1/(5xx7)+1/(7xx9)+1/(9xx11))
    =2xx1/2xx(2/(1xx3)+2/(3xx5)+2/(5xx7)+2/(7xx9)+2/(9xx11))
    =1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11
    =1-1/11 
    =11/11-1/11
    =10/11
     

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

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