Phương trình 3 sin3x + căn bậc hai của 3 cos9x = 1

A. $\left[\begin{array}{l}x=-\frac{\pi }{6}+\frac{k2\pi }{9}\\ x=\frac{7\pi }{6}+\frac{k2\pi }{9}\end{array}\right.(k\in Z)$

B. $\left[\begin{array}{l}x=-\frac{\pi }{9}+\frac{k2\pi }{9}\\ x=\frac{7\pi }{9}+\frac{k2\pi }{9}\end{array}\right.(k\in Z)$

C. $\left[\begin{array}{l}x=-\frac{\pi }{12}+\frac{k2\pi }{9}\\ x=\frac{7\pi }{12}+\frac{k2\pi }{9}\end{array}\right.(k\in Z)$

D. $\left[\begin{array}{l}x=-\frac{\pi }{54}+\frac{k2\pi }{9}\\ x=\frac{\pi }{18}+\frac{k2\pi }{9}\end{array}\right.(k\in Z)$