Given the equation $\displaystyle 2\cos^2x-\cos x-1=0$ find the exact values of x on the interval $\displaystyle [0,2\pi)$

well i tried to take out a $\displaystyle \cos x$ to come up with $\displaystyle \cos(\cos^2x-1)$ and i know that the Pythagorean identity is$\displaystyle \sin^2x=1-\cos^2x$ could anyone help steer me in the right direction