The recurrence relation an=2an−1−2an−2a_n = 2a_{n-1} - 2a_{n-2}an=2an−1−2an−2 has which characteristic roots?
1±i1 \pm i1±i
1±2i1 \pm \sqrt{2}i1±2i
2±i2 \pm i2±i
12(1±i)\frac{1}{\sqrt{2}}(1 \pm i)21(1±i)