Show that if $\displaystyle U_n and V_n $ are solutions of $\displaystyle \Delta^{2} y_{n} + p_{n} \Delta y_{n}+ q_{n}y_{n} = 0 $ and $\displaystyle C_{n}= $ $\displaystyle \left(\begin{array}{cc}U_{n}&Y_{n}\\ \Delta U_{n}&\Delta Y_n \end{array}\right)$, then $\displaystyle \Delta C_{n} + (p_{n} - q_{n})C_{n} = 0 $