A realization of a stable discrete time system is shown in the figure. If the system is excited by a unit step sequence input $x[n ],$ the response $y[n ]$ is
- $4\left(-\dfrac{1}{3}\right)^{n}\:u[n]-5\left(-\dfrac{2}{3}\right)^{n}\:u[n]$
- $5\left(-\dfrac{2}{3}\right)^{n}\:u[n]-3\left(-\dfrac{1}{3}\right)^{n}\:u[n]$
- $5\left(\dfrac{1}{3}\right)^{n}\:u[n]-5\left(\dfrac{2}{3}\right)^{n}\:u[n]$
- $5\left(\dfrac{2}{3}\right)^{n}\:u[n]-5\left(\dfrac{1}{3}\right)^{n}\:u[n]$