Đáp án:
$ x=\dfrac{3^2.5^5}{7^7}$
Giải thích các bước giải:
$a)\left(\dfrac{3}{5}\right)^5x=\left(\dfrac{3}{7}\right)^7\\ \Leftrightarrow x=\dfrac{\left(\dfrac{3}{7}\right)^7}{\left(\dfrac{3}{5}\right)^5}\\ \Leftrightarrow x=\left(\dfrac{3}{7}\right)^7.\left(\dfrac{5}{3}\right)^{5}\\ \Leftrightarrow x=\left(\dfrac{3}{7}\right)^2.\left(\dfrac{3}{7}\right)^5.\left(\dfrac{5}{3}\right)^{5}\\ \Leftrightarrow x=\left(\dfrac{3}{7}\right)^2.\left(\dfrac{5}{7}\right)^5\\ \Leftrightarrow x=\dfrac{3^2.5^5}{7^7}$
