Which of these is a linear homogeneous recurrence relation of degree 2?
an=an−1+an−2a_n = a_{n-1} + a_{n-2}an=an−1+an−2
an=(an−1)2a_n = (a_{n-1})^2an=(an−1)2
an=an−1cdotan−2a_n = a_{n-1} \\cdot a_{n-2}an=an−1cdotan−2
an=an−1+5a_n = a_{n-1} + 5an=an−1+5