If ana_nan is a solution to an=3an−1−2an−2a_n = 3a_{n-1} - 2a_{n-2}an=3an−1−2an−2, which of these must be true?
an=c1(1)n+c2(2)na_n = c_1 (1)^n + c_2 (2)^nan=c1(1)n+c2(2)n
an=c1(3)n+c2(−2)na_n = c_1 (3)^n + c_2 (-2)^nan=c1(3)n+c2(−2)n
an=c1(2)n+c2(−1)na_n = c_1 (2)^n + c_2 (-1)^nan=c1(2)n+c2(−1)n
an=c1(2)n+c2(1)na_n = c_1 (2)^n + c_2 (1)^nan=c1(2)n+c2(1)n