What is the characteristic equation for an=an−1+2an−2+3an−3a_n = a_{n-1} + 2a_{n-2} + 3a_{n-3}an=an−1+2an−2+3an−3?
r3−r2−2r−3=0r^3 - r^2 - 2r - 3 = 0r3−r2−2r−3=0
r3+r2+2r+3=0r^3 + r^2 + 2r + 3 = 0r3+r2+2r+3=0
r3−3r2−2r−1=0r^3 - 3r^2 - 2r - 1 = 0r3−3r2−2r−1=0
r2−r−2=0r^2 - r - 2 = 0r2−r−2=0