7 views

If the region of convergence of $x_1[n]+x_2[n]$ is $\frac{1}{3}<|z|<\frac{2}{3}$, then the region of convergence of $x_1[n]-x_2[n]$ includes

1. $\frac{1}{3}<|z|<3$
2. $\frac{2}{3}<|z|<3$
3. $\frac{2}{3}<|z|<3$
4. $\frac{1}{3}<|z|<\frac{2}{3}$