How to solve recurrence relation ??? The Example is ; Solve the recurrence relation a n + 2a n-1 + 2a n-2 = 0 where n ≥ 2 and a 0 = 1 a 1 = 3 a n = nth order a n-1 = (n-1)th order. a n-2 = (n-2)th order. I've started the solving ; a n = r^n so the equation will be ; r^n + 2r^(n-1) + 2r^(n-2) r^2 + 2r + 2 = 0 I could'nt do anything after find the roots ? What should i do ? Thanks for helping.