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

Toán Lớp 7: tính hợp lý 4 mũ 2 + 4 mũ 4+ 4 mũ 6 + 4 mũ 8 + 4 mũ 10

Toán Lớp 7: tính hợp lý 4 mũ 2 + 4 mũ 4+ 4 mũ 6 + 4 mũ 8 + 4 mũ 10

Comments ( 2 )

  1.                      A = $4^{2}$+$4^{4}$+$4^{6}$ +$4^{8}$+$4^{10}$                 (1)
    ⇔ $4^{2}$ . A = $4^{4}$+$4^{6}$+$4^{8}$ +$4^{10}$+$4^{12}$              (2)
    – Lấy (1) – (2). Ta có:
    15 . A = 4^12 –  4^2 = 4^2  . ( 4^10 – 1 )
    ⇒ A= 1118480
    #Huy

  2.         $\text{A=}$ $4^{2}$+$4^{4}$+$4^{6}$+$4^{8}$+$4^{10}$ (2)
    ⇔$\text{4².A}$=$4^{4}$+$4^{6}$+$4^{8}$+$4^{10}$+$4^{12}$ (1)
    $\text{Lấy (1)-(2) ta có}$
     $\text{15.A=}$ $4^{12}$-$4^{2}$=$4^{2}$.($4^{10}$-1)
    $\text{⇒A=1118480}$
     

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

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