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}-a_{a8}}{2a_g}$ is equal to :

Question

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