If a generating function is A(x)=x1−2x−x2A(x) = \frac{x}{1-2x-x^2}A(x)=1−2x−x2x, which recurrence does it represent?
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−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