Tìm x chăng?
\(\sqrt{4x^2}=6\)
\(\Leftrightarrow4x^2=6^2\)
\(\Leftrightarrow4x^2=36\)
\(\Leftrightarrow x^2=36:4\)
\(\Leftrightarrow x^2=9\)
\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\)
Vậy ..............
\(\sqrt{4x^2}=6\\ \Leftrightarrow2.x=6\\ \Leftrightarrow x=3\)