$$y\left [ n \right ]-ay\left [ n-1 \right ]=b_{0}x\left [ n \right ]-b_{1}x\left [ n-1 \right ]$$
1. $y[n]$ is unaffected by the values of $x\left [ n-k \right ];k>2.$
4. When $x\left [ n \right ]=0,n < 0$, the function $y\left [ n \right];n > 0$ is solely determined by the function $x[n]$.