Given a discrete-time LTI system whose difference equation is given by: y[n] + y[n-2] = 2x[n-1]-x[n-2] with the initial conditions y[-1] = 0, y[-2] = 1 and x[-1] = x[-2] = 0. a) Find the response y[n] of the system to the following input: x[n] = { for n = 0,1,2,...,20 elsewhere using: i. The recur function ii. The filter function b) Using stem and subplot commands to plot the two outputs generated in a). Note: In MATLAB, x[n] can be generated using the command: x = ones (1, 21).