Which of the following is a non-homogeneous linear recurrence relation?
an=an−1+an−2a_n = a_{n-1} + a_{n-2}an=an−1+an−2
an=3an−1+2na_n = 3a_{n-1} + 2^nan=3an−1+2n
an=5an−1a_n = 5a_{n-1}an=5an−1
an=an−1−an−2a_n = a_{n-1} - a_{n-2}an=an−1−an−2