\(\left(\frac{-3}{4}\right)^x:\left(\frac{7}{4}\right)^x=\frac{9}{49}\)
\(\Rightarrow\left(\frac{-3}{4}:\frac{7}{4}\right)^x=\left(\frac{3}{7}\right)^2\)
\(\Rightarrow\left(\frac{-3}{7}\right)^x=\left(\frac{3}{7}\right)^2\)
\(\Rightarrow\left(\frac{-3}{7}\right)^x=\left(\frac{-3}{7}\right)^2\)
\(\Rightarrow x=2\)
Vậy x = 2