If an=c13n+c2(−3)na_n = c_1 3^n + c_2 (-3)^nan=c13n+c2(−3)n, which of the following is the characteristic equation?
r2−9=0r^2 - 9 = 0r2−9=0
r2−3=0r^2 - 3 = 0r2−3=0
r2+9=0r^2 + 9 = 0r2+9=0
r2−6r+9=0r^2 - 6r + 9 = 0r2−6r+9=0