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

Toán Lớp 7: Tìm x ; y `2^(x + 1) . 3^y = 12^x`

Toán Lớp 7: Tìm x ; y
2^(x + 1) . 3^y = 12^x

Comments ( 2 )

  1. 2^{x+1} .3^y=12^x
    <=>2^{x+1} .3^y=2^{2x} .3^x
    <=>\frac{2^{2x}}{2^{x+1}}=\frac{3^y}{3^x}
    <=>2^{x-1}=3^{y-x}
    =>\(\left[\begin{array}{l}x-1=0\\y-x=0\end{array} \right.\) 
    <=>\(\left[ \begin{array}{l}x=1\\x=1\end{array} \right.\) 
    Vậy x=1 và y=1
     

  2. $2^{x + 1}$ . $3^{y}$ = $12^{x}$ => $2^{x+1}$ . $3^{y}$ = $4^{x}$ . $3^{x}$
    => $2^{x+1}$ . $3^{y}$ = ($2^{2}$ )$^{x}$ . $3^{x}$ => x+1 = 2y và y = x
    => x = 1 và y = x. = 1
    Vậy y = 1 ; x = 1

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

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