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