\(\Leftrightarrow\left(\dfrac{3}{4}\right)^x.\left(\dfrac{4}{3}\right)^{\dfrac{4}{x}}=\dfrac{9}{16}\)
\(\Rightarrow\left(\dfrac{3}{4}\right)^x.\left(\dfrac{3}{4}\right)^{-\dfrac{4}{x}}=\left(\dfrac{3}{4}\right)^2\)
\(\Rightarrow\left(\dfrac{3}{4}\right)^{x-\dfrac{4}{x}}=\left(\dfrac{3}{4}\right)^2\)
\(\Rightarrow x-\dfrac{4}{x}=2\)
\(\Rightarrow x^2-2x-4=0\)
Viet: \(x_1+x_2=2\)