Phương trình \[6{\sin ^2}x + 7\sqrt 3 \sin 2x - 8{\cos ^2}x = 6\] có nghiệm là:

A.0     

B.1     

C.2      

D.4

A.\[ - \frac{{5{\pi ^2}}}{{12}}\]

B. \[ - \frac{{5{\pi ^2}}}{{144}}\]

C. \[\frac{{5{\pi ^2}}}{{144}}\]

D. \[\frac{{{\pi ^2}}}{{12}}\]

A.\[m \ne \frac{1}{2}\]

B. \[m = \frac{1}{2}\]

C. \(\left\{ {\begin{array}{*{20}{c}}{\frac{1}{3} < m < 1}\\{m \ne \frac{1}{2}}\end{array}} \right.\)

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D. \[\frac{1}{3} < m < 1\]

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A.\(\left[ {\begin{array}{*{20}{c}}{x = \frac{{k\pi }}{2}}\\{x = \pm \frac{1}{2}arccos( - \frac{1}{6}) + k\pi }\end{array}} \right.(k \in Z)\)

B. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{{k\pi }}{2}}\\{x = \pm \frac{5}{2}arccos( - \frac{1}{6}) + k\pi }\end{array}} \right.(k \in Z)\)

C. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{{k\pi }}{2}}\\{x = \pm \frac{1}{2}arccos( - \frac{1}{3}) + k\pi }\end{array}} \right.(k \in Z)\)

D. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{{k\pi }}{2}}\\{x = \pm \frac{1}{3}arccos( - \frac{1}{6}) + k\pi }\end{array}} \right.(k \in Z)\)

A.0

B.1     

C.2

D.3

A.\(\left[ {\begin{array}{*{20}{c}}{x = \frac{\pi }{3} + k\pi }\\{x = \frac{\pi }{6} + k\pi }\end{array}} \right.(k \in Z)\)

B. \(\left[ {\begin{array}{*{20}{c}}{x = \frac{\pi }{3} + k2\pi }\\{x = \frac{\pi }{6} + k2\pi }\end{array}} \right.(k \in Z)\)

C. \(\left[ {\begin{array}{*{20}{c}}{x = - \frac{\pi }{3} + k\pi }\\{x = - \frac{\pi }{6} + k\pi }\end{array}} \right.(k \in Z)\)

D. \(\left[ {\begin{array}{*{20}{c}}{x = - \frac{\pi }{3} + k2\pi }\\{x = \frac{\pi }{6} + k\pi }\end{array}} \right.(k \in Z)\)

A.\[x = \frac{{k\pi }}{{18}};\,\,x = \frac{{k\pi }}{{22}}\,\,\left( {k \in \mathbb{Z}} \right)\]

B. \[x = \frac{{k\pi }}{9};\,\,x = \frac{\pi }{{44}} + \frac{{k\pi }}{{22}}\,\,\left( {k \in \mathbb{Z}} \right)\]

C. \[x = \frac{\pi }{3} + \frac{{k\pi }}{{18}};\,\,x = \frac{\pi }{{22}} + \frac{{k\pi }}{{22}}\,\,\left( {k \in \mathbb{Z}} \right)\]

D. \[x = \frac{{k\pi }}{3};\,\,x = \frac{\pi }{{44}} + \frac{{k\pi }}{{44}}\,\,\left( {k \in \mathbb{Z}} \right)\]