contestada

Determine whether or not each of the following four examples of the impulse response, h,[n] are stable/unstable and causal/uncausal.
(a) h₁ [n] = (0. 5) ⁿ u[n]
(b) h₂ [n] = - (0. 5) ⁿ u[- n - 1]
(c) h₃ [n] = 2ⁿ u[n]
(d) h₄ [n] = - 2ⁿ u[- n - 1]