What is the characteristic equation for an=an−1a_n = a_{n-1}an=an−1?
r−1=0r - 1 = 0r−1=0
r=0r = 0r=0
r2−1=0r^2 - 1 = 0r2−1=0
r+1=0r + 1 = 0r+1=0