BCNN ( 480 ; 240 ; 720 ) (3x – 8) ^10 = ( 3x – 8 ) ^12

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1. Đáp án:

   $\begin{array}{l}
   480 = {2^5}.3.5\\
   240 = {2^4}.3.5\\
   720 = {2^4}{.3^2}.5\\
    \Rightarrow BCNN\left( {480;240;720} \right) = {2^5}{.3^2}.5 = 1440\\
   {\left( {3x – 8} \right)^{10}} = {\left( {3x – 8} \right)^{12}}\\
    \Rightarrow {\left( {3x – 8} \right)^{10}}.\left( {1 – {{\left( {3x – 8} \right)}^2}} \right) = 0\\
    \Rightarrow \left[ \begin{array}{l}
   3x – 8 = 0\\
   1 – {\left( {3x – 8} \right)^2} = 0
   \end{array} \right.\\
    \Rightarrow \left[ \begin{array}{l}
   x = \frac{8}{3}\\
   3x – 8 = 1\\
   3x – 8 =  – 1
   \end{array} \right. \Rightarrow \left[ \begin{array}{l}
   x = \frac{8}{3}\\
   x = 3\\
   x = \frac{7}{3}
   \end{array} \right.
   \end{array}$

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