\(x^2-16=0\)
\(\Leftrightarrow x^2-4^2=0\)
\(\Leftrightarrow\left(x+4\right)\left(x-4\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-4=0\\x+4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=-4\end{matrix}\right.\)
Vậy \(x=4;-4\)
v~~~ thật thế này cx ko bít làm
ta có :
\(x^2-16=0\Leftrightarrow x^2=16\Leftrightarrow x^2=4^2\Leftrightarrow\left[{}\begin{matrix}x=-4\\x=4\end{matrix}\right.\)
vậy \(x\in\left\{-4;4\right\}\)