\(\sqrt{4x^2}=6\Rightarrow\left|2x\right|=6\Rightarrow\left[{}\begin{matrix}2x=6\\2x=-6\end{matrix}\right.\) \(\Rightarrow x=\pm3\)
b/ ĐKXĐ: \(x\ge0\)
\(\sqrt{16x}=8\Leftrightarrow16x=64\Rightarrow x=4\)
c/ ĐKXĐ: \(x\ge1\)
\(\sqrt{9\left(x-1\right)}=21\Leftrightarrow\sqrt{x-1}=7\Leftrightarrow x-1=49\Rightarrow x=50\)
d/ \(\sqrt{4\left(1-x\right)^2}=6\Leftrightarrow2\left|1-x\right|=6\Leftrightarrow\left|1-x\right|=3\Rightarrow\left[{}\begin{matrix}x=-2\\x=4\end{matrix}\right.\)
e/ \(\sqrt{1-4x+4x^2}=5\Leftrightarrow\sqrt{\left(2x-1\right)^2}=5\Leftrightarrow\left[{}\begin{matrix}2x-1=5\\2x-1=-5\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=3\\x=-2\end{matrix}\right.\)
f/ĐKXĐ: \(x\ge-\frac{1}{2}\)
\(\sqrt{9x^2}=2x+1\Leftrightarrow\left|3x\right|=2x+1\Leftrightarrow\left[{}\begin{matrix}3x=2x+1\\-3x=2x+1\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=1\\x=-\frac{1}{5}\end{matrix}\right.\)
