\(\dfrac{\dfrac{3}{5}.7^2-3.5^6+\dfrac{3}{5}.3^9}{\dfrac{3}{4}.7^2-\dfrac{3}{4}.5^7+\dfrac{3}{4}.3^9}=\dfrac{\dfrac{3}{5}.7^2-\dfrac{3}{5}.5^7+\dfrac{3}{5}.3^9}{\dfrac{3}{4}.7^2-\dfrac{3}{4}.5^7+\dfrac{3}{4}.3^9}\)
\(=\dfrac{\dfrac{3}{5}\left(7^2-5^7+3^9\right)}{\dfrac{3}{4}\left(7^2-5^7+3^9\right)}=\dfrac{3}{5}:\dfrac{3}{4}=\dfrac{3}{5}.\dfrac{4}{3}=\dfrac{4}{5}\)
\(=\dfrac{3\left(\dfrac{1}{5}\cdot49-5^6+\dfrac{1}{5}\cdot3^9\right)}{3\left(\dfrac{1}{4}\cdot7^2-\dfrac{1}{4}\cdot5^7+\dfrac{1}{4}\cdot3^9\right)}=\dfrac{3\cdot\dfrac{-58393}{5}}{3\cdot\dfrac{-58393}{4}}\)
\(=\dfrac{4}{5}\)
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