Giải phương trình: \(2{\cos ^2}x + \sqrt 2 \cos x - 2 = 0\)
A.\(\left[ \begin{array}{l}x = \dfrac{\pi }{4} + k2\pi \\x = - \dfrac{\pi }{4} + k2\pi \end{array} \right.\)
B.\(\left[ \begin{array}{l}x = \dfrac{\pi }{4} + k\pi \\x = - \dfrac{\pi }{4} + k\pi \end{array} \right.\)
C.\(x = \dfrac{\pi }{4} + k2\pi \)
D.\(x = - \dfrac{\pi }{4} + k2\pi \)