Question

tìm x để căn thức sau có nghĩa 
\(\sqrt{x^3-16x}\)

Answer 1

ĐKXĐ: \(x^3-16x>=0\)

=>\(x\left(x^2-4\right)>=0\)

TH1: \(\left[{}\begin{matrix}x>=0\\x^2-4>=0\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x>=0\\\left[{}\begin{matrix}x>=2\\x< =-2\end{matrix}\right.\end{matrix}\right.\Leftrightarrow x>=2\)

TH2: \(\left[{}\begin{matrix}x< =0\\x^2-4< =0\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x< =0\\-2< =x< =2\end{matrix}\right.\)

=>-2<=x<=0