Replace $R_2$ by $R_2+(-2)R_1.$

$\left[\begin{array}{cccccccccc}1& 1& -6& -7& 4& 4& 8& 3& 6& 9\end{array}\right]$

$-4$

$-4$

$2$

$R_2+(-2)R_1=[]$