Asequence {un) is given by the recurrence relation anti un+1 = un + att for n= 1,2,3, and the initial term ui = 3. (a) showing your working, use the recurrence relation to compute un for n = 2,3,4,5. (b) give a proof by induction to show that un= 2 - (n + 2)2-" for all n 2 1.