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

Toán Lớp 6: rút gọn biểu thức :M=1/1.2+1/2.7+1/7.5+1/5.13+…+1/50.97

Toán Lớp 6: rút gọn biểu thức :M=1/1.2+1/2.7+1/7.5+1/5.13+…+1/50.97

Comments ( 2 )

  1. M=1/(1.2)+1/(2.7)+1/(7.5)+1/(5.13)+…+1/(50.97)
    1/2 . M = 1/(1.4)+1/(4.7)+1/(7.10)+1/(10.13)+…+1/(97.100)
    3 . 1/2 . M = 3/(1.4)+3/(4.7)+3/(7.10)+3/(10.13)+…+3/(97.100)
    3/2 . M = 1 – 1/4 + 1/4 -1/7 + 1/7 – 1/10+1/10 – 1/13 +…+ 1/97 – 1/100
    3/2 . M = 1 – 1/100
    3/2 . M = 99/100
    M = 99/100 : 3/2
    M = 33/50
    (Chúc bạn học tốt)
     

  2. M = 1/{1 × 2} + 1/{2 × 7} + 1/{7 × 5} + 1/{5 × 13} + … + 1/{50 × 97}
    1/2 × M = 1/{4 × 7} + 1/{7 × 10} + 1/{10 × 13} + …. + 1/{97 × 100}
    1/2 × 3 × M = 3/{4 × 7} + 3/{7 × 10} + 3/{10 × 13} + … + 3/{97 × 100}
    3/2 × M = 1/1 – 1/4 + 1/4 – 1/7 + 1/7 – 1/10 + 1/10 – 1/13 + … + 1/97 – 1/100
    3/2 × M = 1/1 + 1/4 – 1/4 + 1/7 – 1/7 + 1/10 – 1/10 + 1/13 – 1/13 + … + 1/97 – 1/97 – 1/100
    3/2 × M = 1/1 + 0 + 0 + 0 + 0 + … + 0 – 1/100
    3/2 × M = 1/1 – 1/100
    3/2 × M = 99/100
    => M = 99/100 : 3/2
    M = 198/300 = 33/50
    #dtkc
     

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

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