\(\sqrt{x^2+6x+9}=2x-3\)
\(\Leftrightarrow\left|x-3\right|=2x-3\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=2x-3\\x-3=3-2x\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=2\end{matrix}\right.\)
Vậy ...
\(\sqrt{x^2-6x+9}=2x-3\)\(\Leftrightarrow\sqrt{x^2-2\cdot x\cdot3+3^2}=2x-3\)\(\Leftrightarrow\sqrt{\left(x-3\right)^2}=2x-3\)\(\Leftrightarrow\left\{{}\begin{matrix}x-3=2x-3\left(x-3\ge0\right)\\x-3=3-2x\left(x-3\le0\right)\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x-2x=-3+3\\x+2x=3+3\end{matrix}\right.\)\(\Leftrightarrow\left\{{}\begin{matrix}-x=0\\3x=6\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=0\\x=2\end{matrix}\right.\)
Vậy \(S=\left\{0;2\right\}\)
sửa hàng đầu thành dấu''-'' nhé , mk nhầm
