Một câu thui mà, giúp điiiiii

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Một câu thui mà, giúp điiiiii
mot-cau-thui-ma-giup-diiiiii

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Sigridomena 5 years 2021-05-17T16:54:46+00:00 1 Answers 24 views 0

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  1. Gerda
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    2021-05-17T16:55:51+00:00
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    $3^{x-1}+4.3^{x-2}=\dfrac{7}{243}\\ \Leftrightarrow 3^{x-1}+\dfrac{4}{3}.3^{x-1}=\dfrac{7}{3^5}\\ \Leftrightarrow 3^{x-1}\left(1+\dfrac{4}{3}\right)=\dfrac{7}{3^5}\\ \Leftrightarrow 3^{x-1}.\dfrac{7}{3}=\dfrac{7}{3^5}\\ \Leftrightarrow \dfrac{7}{3.3^{1-x}}=\dfrac{7}{3^5}\\ \Leftrightarrow \dfrac{7}{3^{2-x}}=\dfrac{7}{3^5}\\ \Rightarrow 2-x=5\\ \Leftrightarrow x=-3$

     

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