\(\left(\dfrac{2}{3}\right)^n.\left(\dfrac{3}{4}\right)^n=\dfrac{1}{4}\)
\(\left(\dfrac{2}{3}\cdot\dfrac{3}{4}\right)^n=\dfrac{1}{4}\)
\(\left(\dfrac{1}{2}\right)^n=\dfrac{1}{4}\)
\(\left(\dfrac{1}{2}\right)^n=\left(\dfrac{1}{2}\right)^2\)
\(\Leftrightarrow n=2\)
Vậy n=2