Đáp án:
Giải thích các bước giải:
\[\begin{array}{l}
a)Ta\_{\mathop{\rm co}\nolimits} : - 1 \le sin3x \le 1\\
= > Miny = 2 + 3.( - 1) = - 1 \Leftrightarrow sin3x = - 1 \Leftrightarrow x = - \frac{\pi }{6} + \frac{{k2\pi }}{3}\\
Maxy = 2 + 3.1 = 5 \Leftrightarrow \sin 3x = 1 \Leftrightarrow x = \frac{\pi }{6} + \frac{{k2\pi }}{3}\\
b)y = \sqrt {\frac{{1 - \sin x}}{{1 + \cos x}}} \\
Ta\_co: - 1 \le {\mathop{\rm cosx}\nolimits} \le 1 = > 1 + \cos x \ge 0\\
Dk:\left\{ \begin{array}{l}
1 + \cos x \ne 0\\
\frac{{1 - \sin x}}{{1 + \cos x}} \ge 0
\end{array} \right. = > \left\{ \begin{array}{l}
\cos x \ne - 1\\
1 - \sin x \ge 0
\end{array} \right. = > \left\{ {x \ne \pi + k2\pi } \right.
\end{array}\]
