12 points Using the iterative method (forward or backward substitution) solve the following recurrence relations with the given initial conditions. Show the steps of your calculation. Note: you may use the formulas from Figure 1 (a) an= an-1 + 3, ao-1 (b) an- an-1-n, ao 4 (c) an=2an-1-3, ao=-1 (d) an= 2nan-1,ao=3 Sum Closed Form ark (r * 0) n+1 k=0 n(n1 k2 k3 n(n +1 k=0