A recurrence relation has roots r=1±2r = 1 \pm \sqrt{2}r=1±2. What is the recurrence?
an=2an−1+an−2a_n = 2a_{n-1} + a_{n-2}an=2an−1+an−2
an=2an−1−an−2a_n = 2a_{n-1} - a_{n-2}an=2an−1−an−2
an=an−1+2an−2a_n = a_{n-1} + 2a_{n-2}an=an−1+2an−2
an=2an−1+2an−2a_n = 2a_{n-1} + 2a_{n-2}an=2an−1+2an−2