a: =>căn 3x+19=x+5
\(\Leftrightarrow\left\{{}\begin{matrix}x^2+10x+25=3x+19\\x>=-\dfrac{19}{3}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x^2+7x+6=0\\x>=-\dfrac{19}{3}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(x+1\right)\left(x+6\right)=0\\x>=-\dfrac{19}{3}\end{matrix}\right.\Leftrightarrow x\in\left\{-6;-1\right\}\)
b: =>\(\sqrt{4x}=\sqrt{9x-3}\)
=>9x-3=4x
=>5x=3
=>x=3/5