\(a,\sqrt{x^2-10x+25}=x-2\\ ĐK:x-2\ge0\Leftrightarrow x\ge2\\ \sqrt{x^2-10x+25}=x-2\\ \Leftrightarrow x^2-10x+25=x^2-4x+4\\ \Leftrightarrow x^2-x^2-10x+4x=4-25\\ \Leftrightarrow-6x=-21\\ \Leftrightarrow x=\dfrac{7}{2}\left(tm\right)\\ Vậy.S=\left\{\dfrac{7}{2}\right\}\\ b,\sqrt{x+2}+\sqrt{9x+8}+\sqrt{4x+8}=2\\ \Leftrightarrow\sqrt{x+2}+3\sqrt{x+2}+2\sqrt{x+2}=2\\ \Leftrightarrow6\sqrt{x+2}=2\\ \Leftrightarrow\left[{}\begin{matrix}x+2\ge0\\\sqrt{x+2}=\dfrac{1}{3}\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x\ge-2\\x+2=\dfrac{1}{9}\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x\ge-2\\x=\dfrac{1}{9}-2\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x\ge-2\\x=-\dfrac{17}{9}\left(tm\right)\end{matrix}\right.\\ Vậy.S=\left\{-\dfrac{17}{9}\right\}\)
