\(\Leftrightarrow\left[{}\begin{matrix}x^2-5=0\\x+3=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2=5\\x=-3\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-\sqrt{5}\\x=\sqrt{5}\\x=-3\end{matrix}\right.\)
\(=>\left[{}\begin{matrix}x^2-5=0\\x+3=0\end{matrix}\right.< =>\left[{}\begin{matrix}x=\pm\sqrt{5}\\x=-3\end{matrix}\right.\)
vậy.....
⇔[x2−5=0x+3=0⇔[x2−5=0x+3=0
⇔[x2=5x=−3⇔[x2=5x=−3
⇔⎡⎢⎣x=−√5x=√5x=−3
<=>\(\left[{}\begin{matrix}x^2-5=0\\x+3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{5}\\x=-\sqrt{5}\\x=-3\end{matrix}\right.\)
Vậy S=\(\left\{-3,\sqrt{5},-\sqrt{5}\right\}\)
