A sequence has closed form an=3⋅4n+2⋅5na_n = 3 \cdot 4^n + 2 \cdot 5^nan=3⋅4n+2⋅5n. Which recurrence relation does it satisfy?
an=9an−1−20an−2a_n = 9a_{n-1} - 20a_{n-2}an=9an−1−20an−2
an=9an−1+20an−2a_n = 9a_{n-1} + 20a_{n-2}an=9an−1+20an−2
an=4an−1+5an−2a_n = 4a_{n-1} + 5a_{n-2}an=4an−1+5an−2
an=20an−1−9an−2a_n = 20a_{n-1} - 9a_{n-2}an=20an−1−9an−2