Question

Ghi giúp em cái đk ạ

Answer 1

\(x\ge4\)

Answer 2

\(\sqrt{x^2-16}-2\sqrt{x-4}=0\left(đk:x\ge4\right)\)

\(\Leftrightarrow\sqrt{\left(x-4\right)\left(x+4\right)}-2\sqrt{x-4}=0\)

\(\Leftrightarrow\sqrt{x-4}\left(\sqrt{x+4}-2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x-4}=0\\\sqrt{x+4}=2\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x-4=0\\x+4=4\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=4\left(tm\right)\\x=0\left(ktm\right)\end{matrix}\right.\)