a, \(\sqrt{x^2}=4\Leftrightarrow|x|=4\Leftrightarrow x=\pm4\)
b, ĐKXĐ: \(x\ge\frac{4}{3}\)
\(\sqrt{3x-4}=3\Leftrightarrow3x-4=9\Leftrightarrow x=\frac{13}{3}\left(tm\right)\)
c, \(\sqrt{\left(5-3x\right)^2}=9\Leftrightarrow|5-3x|=9\)
\(\Leftrightarrow\left[{}\begin{matrix}5-3x=9\\5-3x=-9\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\frac{4}{3}\\x=\frac{14}{3}\end{matrix}\right.\)