The set of all values of \( \lambda \) for which the equation \( \cos^{2}2x-2\sin^{4}x-2\cos^{2}x=\lambda \) has a real solutions \( x \), is:
\( [ -2,-1] \)
\( [ -1,-\dfrac{1}{2} ] \)
\( [ -\dfrac{3}{2},-1 ] \)
\( [ -2,-\dfrac{3}{2} ] \)