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

Toán Lớp 6: B=4+4³+4⁵+…+4⁵⁹ . Mn gấp giúp e ạ ,e đg cần ạ

Toán Lớp 6: B=4+4³+4⁵+…+4⁵⁹ . Mn gấp giúp e ạ ,e đg cần ạ

Comments ( 2 )

  1. B=4+4^3+4^5+. . .+4^59
    4^2B=4^3+4^5+4^7+. . .+4^61
    4^2B-B=(4^3+4^5+4^7+. . .+4^61)-(4+4^3+4^5+. . .+4^59)
    15B=4^61-4
    B=$\dfrac{4^{61} – 4}{15}$ 

  2. B = 4 + 4^{3} + 4^{5} +…+ 4^{59}
    4^{2} . B = 4^{3} + 4^{5} + 4^{7} +…+ 4^{61}
    16B = 4^{3} + 4^{5} + 4^{7} +…+ 4^{61}
    16B – B = (4^{3} + 4^{5} + 4^{7} +…+ 4^{61}) – (4 + 4^{3} + 4^{5} +…+ 4^{59})
    15B = 4^{61} – 4
    B = {4^{61} – 4}/15
    $\text{Vậy}$ B = {4^{61} – 4}/15
     

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