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

Toán Lớp 7: $3^{x}$ + $3^{x+2}$ = 7290 Giúp mình với ạ

Toán Lớp 7: $3^{x}$ + $3^{x+2}$ = 7290
Giúp mình với ạ

Comments ( 2 )

  1. \(3^x + 3^{x+2} = 7290\\\Leftrightarrow 3^x + 3^x\times 3^2=7290\\\Leftrightarrow 3^x(1+3^2) = 7290\\\Leftrightarrow 10 \times 3^x = 7290 \\\Leftrightarrow 3^x = 729 \\\Leftrightarrow 3^x = 3^6\\\Leftrightarrow x=6\)
     

  2. Answer
    ${3^x+}$ $3^{x+2}=7290$
    ${10.3^x=7290}$
    $\dfrac{10.3^x}{10}=$ $\dfrac{7290}{10}$
    ${3^x=729}$
    $x={6}$
     

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

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