a/ \(\sqrt{\left(x-3\right)^2}=9\)\(\Leftrightarrow\left|x-3\right|=9\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=9\\x-3=-9\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=12\\x=-6\end{matrix}\right.\)
vậy x=12 hoặc x=-9
b/\(\sqrt{4x^2+4x+1}=6\)\(\Leftrightarrow\sqrt{\left(2x+1\right)^2}=6\)
\(\Leftrightarrow\left|2x+1\right|=6\Leftrightarrow\left[{}\begin{matrix}2x+1=6\\2x+1=-6\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=\frac{5}{2}\\x=-\frac{7}{2}\end{matrix}\right.\)
vậy x=5/2 hoặc x=-7/2
\(a\)) \(\sqrt{\left(x-3\right)^2}=9\Leftrightarrow\left|x-3\right|=9_{ }\)
\(\Leftrightarrow\left\{{}\begin{matrix}x-3=9\\x-3=-9\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=12\\x=-6\end{matrix}\right.\)
\(b\)) \(\sqrt{4x^2+4x+1}=6\Leftrightarrow\sqrt{\left(2x+1\right)^2}=6\)
\(\Leftrightarrow\left|2x+1\right|=6\Leftrightarrow\left\{{}\begin{matrix}2x+1=6\\2x+1=-6\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x=5\\2x=-7\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\frac{5}{2}\\x=\frac{-7}{2}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=2,5\\x=-3,5\end{matrix}\right.\)
