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

Toán Lớp 6: A = `2/3` + `2/15` + `2/35` + `2/63` + `2/99` + `2/143`

Toán Lớp 6: A = 2/3 + 2/15 + 2/35 + 2/63 + 2/99 + 2/143

Comments ( 2 )

  1. Giải đáp + Lời giải và giải thích chi tiết:
    A=(2)/(3)+(2)/(15)+(2)/(35)+(2)/(63)+(2)/(99)+(2)/(143)
    =(2)/(1.3)+(2)/(3.5)+(2)/(5.7)+(2)/(7.9)+(2)/(9.11)+(2)/(11.13)
    =1-(1)/(3)+(1)/(3)-(1)/(5)+(1)/(5)-(1)/(7)+(1)/(7)-(1)/(9)+(1)/(9)-(1)/(11)+(1)/(11)-(1)/(13)
    =1-(1)/(13)
    =(13)/(13)-(1)/(13)=(12)/(13)
    Vậy A=(12)/(13)
     

  2. A= 2/3 + 2/15 + 2/35 + 2/63 + 2/99 + 2/143
    = \frac{2}{1.3} + \frac{2}{3.5}+ \frac{2}{5.7} + \frac{2}{7.9}+ \frac{2}{9.11} + \frac{2}{11.13}
    =(1 – 1/3) + ( 1/3 – 1/5) + (1/5 – 1/7) + (1/7 – 1/9) + (1/9 – 1/11) + (1/11 – 1/13)
    = 1 – 1/13
    = 13/13 – 1/13
    = 12/13
    Vậy A = 12/13

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

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