2. Determine whether the following signals are periodic and state their fundamental period if they are periodic, (a) x1[n] = u[n+1] + u[1 − n] where u[n] 1∞ = (b) x2[n] = ∞ d[n – 6k] – d[n – 2 – 6k] - 1, n ≥0 [0, n < 0