a. \(5\sqrt{2x}+1=21\left(ĐK:x\ge0\right)\)
<=> \(5\sqrt{2x}=20\)
<=> \(\sqrt{2x}=4\)
<=> 2x = 16
<=> x = 8 (TM)
b. \(\sqrt{9x^2-6x+1}=2\)
<=> \(\sqrt{\left(3x-1\right)^2}=2\)
<=> \(\left|3x-1\right|=2\)
<=> \(\left[{}\begin{matrix}3x-1=2\left(x\ge\dfrac{1}{3}\right)\\3x-1=-2\left(x< \dfrac{1}{3}\right)\end{matrix}\right.\)
<=> \(\left[{}\begin{matrix}x=1\left(TM\right)\\x=-\dfrac{1}{3}\left(TM\right)\end{matrix}\right.\)
a) \(đk:x\ge0\)
\(pt\Leftrightarrow5\sqrt{2x}=20\Leftrightarrow\sqrt{2x}=4\)
\(\Leftrightarrow2x=16\Leftrightarrow x=8\left(tm\right)\)
b) \(pt\Leftrightarrow\sqrt{\left(3x-1\right)^2}=2\)
\(\Leftrightarrow\left|3x-1\right|=2\)
\(\Leftrightarrow\left[{}\begin{matrix}3x-1=2\\3x-1=-2\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{1}{3}\end{matrix}\right.\)
