<=>$sin(2x+\frac{\pi}{6})=-\frac{\sqrt{2}}{2}$
<=>$2x+\frac{\pi}{6}=-\frac{\pi}{4}+k2\pi$ hoặc $2x+\frac{\pi}{6}=\frac{5\pi}{4}+k2\pi$
<=>$x=-\frac{5\pi}{24}+k\pi$ hoặc $x=\frac{13\pi}{24}+k\pi$
x thuộc $[-5\pi;5,5\pi]$
*)$-5 \pi \leq -\frac{5\pi}{24}+k\pi \leq 5,5 \pi$
giải bất => k nguyên
*) $-5\pi \leq \frac{13\pi}{24}+k\pi \leq 5,5 \pi$ tương tự