$y = \sqrt{3 - 2\sin^22x} + 4$
$TXD: D = R$
Ta có:
$0 \leq \sin^22x \leq 1$
$\Leftrightarrow -2 \leq -2\sin^22x \leq 0$
$\Leftrightarrow 1 \leq 3 - 2\sin^22x \leq 3$
$\Leftrightarrow 1 \leq \sqrt{3 - 2\sin^22x} \leq \sqrt3$
$\Leftrightarrow 5 \leq \sqrt{3 - 2\sin^22x} + 4\leq \sqrt3 + 4$
Hay $5 \leq y \leq \sqrt3 + 4$
Vậy $\min y = 5 \Leftrightarrow \sin^22x = \pm \Leftrightarrow x = \dfrac{\pi}{4} + k\dfrac{\pi}{2}$
$\max y = \sqrt3 + 4 \Leftrightarrow \sin2x = 0 \Leftrightarrow x = k\pi \quad (k \in \Bbb Z)$
