Ta có: \(\left(x-3\right)^2=9-x^2\)
\(\Leftrightarrow\left(x-3\right)^2-\left(9-x^2\right)=0\)
\(\Leftrightarrow\left(x-3\right)^2-\left(3-x\right)\left(3+x\right)\)
\(\Leftrightarrow\left(3-x\right)^2-\left(3-x\right)\left(3+x\right)=0\)
\(\Leftrightarrow\left(3-x\right)\left(3-x-3-x\right)=0\)
\(\Leftrightarrow\left(3-x\right)\cdot\left(-2x\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}3-x=0\\x=0\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=0\end{matrix}\right.\)
Vậy: \(x\in\left\{0;3\right\}\)
