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