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

Toán Lớp 6: A=5^0+5^1+5^2+…+5^39 nhanh vs ak

Toán Lớp 6: A=5^0+5^1+5^2+…+5^39 nhanh vs ak

Comments ( 2 )

  1. A = 5^{0} + 5^{1} + … + 5^{39}
    5A = 5 . (5^{0} + 5^{1} + … + 5^{39})
    5A = 5^{1} + 5^{2} + … + 5^{40}
    5A – A = (5^{1} + 5^{2} + … + 5^{40}) – (5^{0} + 5^{1} + … + 5^{39})
    4A = 5^{40} – 5^{0}
    A = {5^{40} – 5^{0}}/4
    A = {5^{40} – 1}/4
    $\text{Vậy}$ A = {5^{40} – 1}/4
     

  2. A = 5^0 + 5^1 + 5^2 + …. + 5^39
    5A = 5^1 + 5^2 + 5^3 + …. + 5^40
    5A – A = ( 5^1 + 5^2 + 5^3 + …. + 5^40 ) – ( 5^0 + 5^1 + 5^2 + …. + 5^39 )
    4A = 5^40 – 5^0
    4A = 5^40 – 1
    A = ( 5^40 – 1 )/4
    Vậy , A = ( 5^40 – 1 )/4 .

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

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