Let $\alpha$ and $\beta$ be the roots of equation $x^2-6x-2 =0$. If $a_n = \alpha ^n -\beta^n$ , for $n \geq 1$, then the value of $\large\frac{a_{10}-2_{a8}}{2_{a9}}$ is equal to :

Question

$\begin{array}{1 1} 3 \\ -3 \\ 6 \\ -6 \end{array} $