Đáp án:
\(\left[ \begin{array}{l}
x \ne \dfrac{\pi }{2} + k2\pi \\
x \ne - \dfrac{\pi }{6} + k2\pi \\
x \ne - \dfrac{{5\pi }}{6} + k2\pi
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
y = \dfrac{{\sqrt 2 - \sin 3x}}{{\cos 2x + \sin x}}\\
DK:\cos 2x + \sin x \ne 0\\
\to 1 - 2{\sin ^2}x + \sin x \ne 0\\
\to \left[ \begin{array}{l}
\sin x \ne 1\\
\sin x \ne - \dfrac{1}{2}
\end{array} \right.\\
\to \left[ \begin{array}{l}
x \ne \dfrac{\pi }{2} + k2\pi \\
x \ne - \dfrac{\pi }{6} + k2\pi \\
x \ne - \dfrac{{5\pi }}{6} + k2\pi
\end{array} \right.
\end{array}\)
