Phương trình 

Câu hỏi: Phương trình $3\sin 3x+\sqrt{3}\cos 9x=1+4{\sin }^{3}3x$ là

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