Question

Answer 1

a) ĐKXĐ: \(-9x-2\ge0\Leftrightarrow-9x\ge2\Leftrightarrow x\le-\dfrac{2}{9}\)

b) ĐKXĐ: \(5-7x< 0\Leftrightarrow5< 7x\Leftrightarrow x>\dfrac{5}{7}\)

c) ĐKXĐ: \(\left\{{}\begin{matrix}7-2x\ge0\\x+3>0\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}2x\le7\\x>-3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\le\dfrac{7}{2}\\x>-3\end{matrix}\right.\Leftrightarrow-3< x\le\dfrac{7}{2}\)

d) ĐKXĐ: \(\left\{{}\begin{matrix}x\ge0\\\sqrt{x}-3\ne0\\\sqrt{x}-1\ne0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\ge0\\x\ne9\\x\ne1\end{matrix}\right.\)

e) ĐKXĐ: \(\left\{{}\begin{matrix}x\ge0\\\sqrt{x}-5\ne0\\\sqrt{x}+4\ne0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\ge0\\x\ne25\end{matrix}\right.\)