Toán Lớp 7: tìm số nguyên x: 7^x+1/49^x= 49^2
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Toán Lớp 7: tìm số nguyên x: 7^x+1/49^x= 49^2
Comments ( 2 )
\frac{{{7^{x + 1}}}}{{{{49}^x}}} = {49^2}\\
\Leftrightarrow {7^{x + 1}} = {7^{2x}}{.7^4}\\
\Leftrightarrow {7^{x + 1}} = {7^{2x + 4}}\\
\Leftrightarrow x + 1 = 2x + 4\\
\Leftrightarrow x = – 3\\
Vậy\,x = – 3
\end{array}$